Cotton Issue - LSU AgCenter/media/system/7/5/9/7/... · Louisiana’s cotton farms have changed dramatically in the past 50 years. In the early 1950s, the average cotton farmer grew

Louisiana Agriculture, Spring 2003 1

Spring 2003Vol. 46, No. 2

Cotton IssueCotton Issue

2 Louisiana Agriculture, Spring 2003

EDITORIAL BOARD:David J. Boethel (Chairman)Linda Foster BenedictBarbara Groves CornsJane HoneycuttTheresia LavergneRay McClainKenneth W. PaxtonT. Eugene ReaganJohn K. Saichuk

Published quarterly by the LouisianaAgricultural Experiment Station, LouisianaState University Agricultural Center,Baton Rouge, Louisiana. Subscriptions arefree. Send requests and any comments orquestions to:

Linda Foster Benedict, EditorLouisiana AgricultureP.O. Box 25100Baton Rouge, LA 70894-5100

phone (225) 578-2263fax (225) [email protected]

www.lsuagcenter.com

EDITOR: Linda Foster Benedict

DESIGNER: Barbara Groves Corns

PHOTO EDITOR: John Wozniak

CONTRIBUTORS: Rick Bogren,Mark Claesgens, A. Denise Coolmanand Jane Honeycutt

The mention of a pesticide or use of a trade namefor any product is intended only as a report ofresearch and does not constitute an endorsementor recommendation by the Louisiana AgriculturalExperiment Station, nor does it imply that a men-tioned product is superior to other products of asimilar nature not mentioned. Uses of pesticidesdiscussed here have not necessarily been approvedby governmental regulatory agencies. Informationon approved uses normally appears on the manu-facturer’s label.

Material herein may be used by the press, radio andother media provided the meaning is not changed.Please give credit to the author and to the publica-tion for any material used.

LSU AgCenterWilliam B. Richardson, Chancellor

William H. Brown, Vice Chancellorand Director of Research

Paul D. Coreil, Vice Chancellorand Director of Extension

The Louisiana Agricultural Experiment Stationprovides equal opportunitiesin programs and employment.

New Research Tool – PDALSU AgCenter scientists have found a new tool for their precision agriculture

research – the personal digital assistant, also known as the PDA.This small hand-held device that most people use to manage their schedules

can also be used for global positioning information. The software that providesthis information also shows a map on the PDA’s screen.

“We use the PDAs for navigating within a field,” said Ralph Bagwell, associateprofessor at the Macon Ridge Research Station, near Winnsboro, La.

Researchers can count insects at that location, for example, and record thisdata as they develop a prescription for pesticide application.

“This is off-the-shelf technology, affordable and easy-to-use for the farmer,”Bagwell said.

Researchers are exploring how to most effectively use this technology as partof the research project described starting on page 9 of this issue.

AgCenter Cotton Lives OnIn Nematode-tolerant Variety

Stoneville Pedigreed Seed Co. is marketing a nematode-tolerant cottonvariety that has its roots in an LSU AgCenter variety. Stoneville developed thevariety ST5599BR from germplasm of LA887, a cotton variety owned by the LSUAgCenter and developed by Jack Jones, a professor who is now retired. Thecompany added two genes. One, called Bollgard, protects the plants from certaininsect pests, and another provides tolerance for the herbicide Roundup.

“I’m proud to see Jack Jones’ original LA887 germplasm, which was successfulin its own right, get another chance to contribute to southern producers throughthis new transgenic variety,” said Bill Brown, vice chancellor for research. “Itproves to be an enduring, widely adapted germplasm base.”

Sanders, BurtsNamed Endowed Professors

Two AgCenter faculty members are now endowed professors, thanks to thegenerosity of Evelyn Edmiston Howell of Houston, Texas. Dearl Sanders, weedscientist and coordinator of the Idlewild Research Station, near Clinton, wasnamed the Floyd S. Edmiston Sr. Professor in Agriculture and Natural ResourceManagement, and Diane Burts was named the Grace Drews Lehmann Professorin Human Ecology. Howell designated Sanders’ professorship in memory of herfather, Floyd S. Edmiston Sr. He was a long-time county agent in Louisiana. Howellgave Burts’ professorship in memory of Grace Drews Lehmann, who wasHowell’s classmate in home economics at LSU.

LSU AgCenter scientists are experimenting with technology that will make itpossible for aerial applicators to spray precisely what’s needed over everysquare foot of a field. This will be good for the aerial applicator business as wellas for farmers. See story on page 9. Photo by John Wozniak.

ON THE COVER



Page 18

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SCIENCE NOTES

14 Cotton HistoryDonald J. Boquet, B. Rogers Leonard and W. David Caldwell

17 Insecticide Resistance Monitoring Programs in Louisiana CottonStephen Micinski, Donald R. Cook, B. Rogers Leonard, Ralph D. Bagwell, Eugene Burris andAlexander M. Stewart

21 Effect of Soil-applied Insecticides on Tarnished Plant BugsDonald R. Cook, Eugene Burris and B. Rogers Leonard

29 Tillage and Cover Crop Effects on Herbicide DegradationLewis Gaston

35 Effects of Pre-plant Application of 2,4-D on CottonDonnie K. Miller, P. Roy Vidrine, Steve T. Kelly and Rebecca G. Frederick

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CONTENTS

4 PERSPECTIVE - Cotton: The Fabric of Louisiana AgricultureRobert L. “Bob” Hutchinson

6 OVERVIEW - Louisiana: A Leader in Cotton ResearchDonald J. Boquet and B. Rogers Leonard

9 Precision Agriculture Aids Cotton Pest ManagementRalph D. Bagwell, B. Rogers Leonard, Jay W. Hardwick, Edwards Barham, Dale Magoun,Randy Price, Robert G. Downer and Kenneth W. Paxton

11 Using Remote Sensing and GPS in Nematode ControlEugene “Gene” Burris, Richard Costello, Boyd Padgett, Charles Overstreetand Maurice Wolcott

13 Improving Cotton Varieties in LouisianaW. David Caldwell, Gerald O. Myers, Steve Hague and James A. Hayes

15 Economics of Technology Use in CottonKenneth W. Paxton

18 Stink Bug Damage Increases in Louisiana CottonMelissa M. Willrich and B. Rogers Leonard

20 Tarnished Plant Bug Problems and Weed Host ControlRichard Costello, Eugene Burris, Gordon Snodgrass and William Scott

22 Managing Fusarium Wilt/Root-knot Nematode ComplexPatrick D. Colyer and Philip R.Vernon

24 Fungus Helps Control Louisiana Cotton AphidsRobert H. Jones, B. Rogers Leonard and Ralph D. Bagwell

26 Poultry Litter Increases Cotton YieldsEddie P. Millhollon, James L. Rabb, Jose F. Liscano and Russell A. Anderson

28 Cotton Defoliation: The Science of the ArtAlexander M. “Sandy” Stewart, Donnie K. Miller and Joel C. Faircloth

30 Irrigating Cotton on Alluvial Soils in LouisianaSteve Hague, Alphonse Coco and Donald J. Boquet

32 Conservation Tillage, Cover Crop BMPs for CottonDonald J. Boquet, Robert L. Hutchinson and Kenneth W. Paxton

34 Nontransgenic Cotton Response to Off-target HerbicidesDonnie K. Miller, Robert G. Downer, Steve T. Kelly and P. Roy Vidrine

Volume 46, Number 2, Spring 2003

Page 15

Assuring Our Future Through Scientific Research and Education



PERSPECTIVE

or more than 100 years cotton hasbeen the most important crop grown innortheast Louisiana. At one time cottonwas grown all across the state, but overthe years it has become increasinglyconcentrated in the northeast partbecause of more favorable environmen-tal conditions and because other crops,especially sugarcane and rice, arepreferred in south Louisiana. For mostof the communities in northeasternLouisiana, cotton production and relatedbusinesses constitute the foundation ofthe economy.

The largest acreage ever producedin Louisiana was planted in 1930 (1.95million acres), and the lowest acreagewas in 1975 (310,000 acres). In the lastfive years, acreage has ranged from610,000 to 849,000, with an averagefarm gate value of more than $270million annually.

About 80 percent of the state’scotton crop is grown on the alluvial soilsbordering the Mississippi and OuachitaRivers and the loess (wind-deposited)soils of the geological formation knownas the Macon Ridge. About 20 percentis grown on Red River alluvial soils innorthwest and central Louisiana.

Dramatic changesLouisiana’s cotton farms have

changed dramatically in the past 50years. In the early 1950s, the averagecotton farmer grew fewer than 20 acresof cotton. During the 1960s and 1970s,farms became much more mechanized,and effective pesticides were developedto reduce the need for manual labor fortillage, planting, weed control, insecti-cide application and, perhaps mostimportant, harvesting. The mechanicalcotton picker revolutionized the harvestprocess and increased the efficiency ofcotton farmers. By the late 1970s, asingle farmer was able to manage morethan 185 acres of cotton. The trendtoward larger and more mechanized

Cotton:The Fabric of Louisiana AgricultureRobert L. “Bob” Hutchinson

farm units has continued, and today atypical farmer grows 400 to 500 acresof cotton with little seasonal labor.

Cotton yields have also increasedgradually during this period. Averageyield in the early 1950s was about 375pounds of lint per acre compared toabout 660 pounds for 1997 to 2001.Some farmers consistently producemore than 1,000 pounds per acre.

LSU AgCenter’s roleFor many years Louisiana’s cotton

producers have depended heavily on theLouisiana Agricultural ExperimentStation and Louisiana CooperativeExtension Service of the LSU AgCenterto supply research-based information toincrease yields, reduce production costsand minimize losses from a myriad ofinsects, weeds, nematodes and plantdiseases.

Most of the applied field experi-ments are conducted at four branchresearch stations—Northeast at St.Joseph, Macon Ridge at Winnsboro,Red River at Bossier City and Dean Leeat Alexandria. The research conducted atthese locations is often performed incooperation with researchers from otherresearch stations and scientists fromseveral campus-based departments.Numerous basic or fundamental re-search projects are conducted in the

AgCenter’s campus-based departmentsand laboratories. In addition, much ofthis research is conducted in cooperationwith researchers from other land-grantuniversities as well as state and federalagencies.

Funding sourcesMost of the funds needed to support

AgCenter cotton research projects areprovided by Louisiana’s taxpayersthrough appropriations from the statelegislature; however, cotton producersin Louisiana provide significant fundingto support research through a check-offprogram jointly administered byLouisiana’s cotton producers and CottonIncorporated. In addition, significantgrant funding is received through jointprojects with other universities, privatecompanies and various governmentagencies. Grant support from all of thesesources has grown significantly and hasbecome an indispensable part of thecotton research budget.

Competitive productionAgCenter researchers and educators

have done a commendable job ofsolving problems, developing newtechnology to increase productivityand helping producers incorporate thesetools into their farming systems. Thisrelationship has helped Louisiana’scotton farmers remain competitivethrough many difficult challenges.

Nevertheless, the cotton industrynow faces many serious challenges andproblems that must be met and over-come if this industry is to remain viable.Plant breeding and variety testingprograms must be fully funded andequipped to develop new germplasmand varieties that are adapted toLouisiana’s environmental conditions,resistant to damage from various pests,with high yield potential and that exhibitfiber traits demanded by modern highspeed textile manufacturing machinery.Cotton fiber data from the U.S. Depart-ment of Agriculture’s Cotton ClassingOffice in Rayville, La., suggests thatfiber length (staple) has declined in the

Robert L. Hutchinson, Director, North CentralRegion, LSU AgCenter, Winnsboro, La. Robert L. Hutchinson

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prices for inputs have risen steadily.Strict environmental regulations havereduced the number of effective pesti-cides available to producers to manageinsects, weeds and insects. To makematters worse, the new materials aretypically much more expensive thanthe older materials and have a muchnarrower spectrum of activity andshorter residual efficacy.

The Boll Weevil EradicationProgram administered by the LouisianaDepartment of Agriculture and Forestry

has been extremely successful ineliminating this pest from much of thestate’s production areas. In 2004, theentire state should reach weevil-freestatus and enter a maintenance programto prevent re-infestation. Although thisprogram is a tremendous asset to cottonproducers, most of the insect manage-ment guidelines will need to be revisedto address new pest concerns in post-eradication cotton fields.

Louisiana water quality regulationswill likely place additional constraintson producers and require adoption ofstrict conservation tillage practices andprecision inputs of fertilizers andpesticides to minimize adverse effectson water bodies. Increased competitionfrom foreign producers and syntheticfibers will require cotton breeders todevelop new cotton varieties with

past 15 years while coarseness(micronaire) has increased. As a result,in recent years a high percentage of ourcotton is discounted heavily because thefibers are too coarse and too short.Cotton breeding programs that empha-size fiber quality improvement as wellas yield can address these problemseffectively.

Numerous agronomic studies haverefined recommendations for fertiliza-tion, irrigation, planting date, rowspacing, crop rotation, cover crops,tillage and other inputsto improve the biologi-cal efficiency of cottonwhile minimizingproduction costs.Although great strideshave been made,considerable research isneeded to fully realizethe economic andenvironmental benefitsof these practices.

New weed andinsect managementprograms that usetransgenic (geneticallyengineered) cottonvarieties and newclasses of pesticideshave provided powerfultools to minimizeeconomic losses fromweeds and insectswhile enhancing safetyto humans, animals andthe environment.Furthermore, in thepast 15 to 20 years,AgCenter researchershave gained nationaland international recognition as leadersin the development of cotton productionsystems, including conservation tillage,that conserve natural resources andprotect the environment. Much of thisresearch has been used to develop bestmanagement practices, known as BMPs,that have been adopted by most cropproducers. More research is needed tointegrate all of these practices andtechnologies for the maximum benefitto producers and the environment.

ChallengesMany challenges lie ahead that

threaten the viability of the cottonindustry in Louisiana and across theCotton Belt. Because of increasedinternational production and competi-tion, prices for cotton have reached thelowest levels in several decades, while

Photo by Robert L. Hutchinson

improved staple length, fineness,strength and uniformity. Increasedenvironmental regulation and expenseof pesticides will require geneticists andbreeders to develop transgenic varietiesthat resist damage from a wider range ofpests and allow the use of safer andmore economical weed control pro-grams. Finally, newly initiated precisionagriculture research in Louisiana willhelp producers target expensive inputsto specific areas in fields that providepositive net returns rather than applying

these inputs to areas less likely toprovide a positive return. This researchhas tremendous potential to increaseprofitability of producers while reducingthe need for pesticides, fertilizer andother inputs.

Cotton research programs of thepast have helped to increase yields andprofitability of cotton while conservingour soil and water resources. Futureresearch programs will continue todevelop new technology to address thechallenges as long as adequate fundingis provided to support these efforts. Thegreatest beneficiaries of these effortswill be the consumers of all the productsderived from cotton lint and seeds andthe numerous communities in northLouisiana, where economic survivaldepends on cotton production, ginningand warehousing.

Conservation tillage has been a primary focus of LSU AgCenter research. This is a spray rig designed toaccurately apply herbicides as a directed spray beneath the cotton plants and to the row middles to controlweeds with no injury to the cotton plants. This method minimizes soil disturbance and reduces soil erosion.


Louisiana:A Leader in Cotton ResearchDonald J. Boquet and B. Rogers Leonard

OVERVIEW

espite its success throughouthistory, cotton as a crop in the U.S.suffers from many problems for manydifferent reasons. There are seedling,stem, root and boll rot diseases, adiverse group of insect species that feedon leaves, plant juices, immature fruitand bolls, and dozens of competingweed species. Adverse weather in earlyspring is hard on this tropical plant, andrainy periods during late summer andfall often cause yield losses through bollrot and delayed harvest. Costs ofproduction for cotton are among thehighest for agronomic crops, but pricesreceived for cotton in the past severalyears were lower than in the 1960s.

Research-based information andtechnology developed by the LSUAgCenter have been important factors inmaintaining profitability in the Louisi-ana cotton industry. In 1929, a group ofnorth Louisiana cotton farmers whorecognized the need for problem-solvingresearch purchased land near St. Josephin the Mississippi River Delta anddonated it to the Louisiana AgriculturalExperiment Station. This station, knowntoday as the Northeast Research Station,has continuously conducted research onthe Mississippi River alluvial soils andis internationally recognized as one ofthe leading cotton research organiza-tions in the country. In 1958, theNortheast Research Station established asubstation in Winnsboro on loess soils(wind-deposited silt loam), known todayas the Macon Ridge Research Station.

Another research station active incotton research is the Red River Re-search Station near Bossier City.Established in 1948, the Red RiverStation is uniquely situated to conductresearch in two areas of consequence tothe region—cotton insect pests andpoultry litter. Evaluation of the technol-ogy to control insect pests with lessreliance on insecticides is one of its

missions. Northwest Louisiana is alsoproximate to extensive poultry produc-tion that generates thousands of tons ofanimal waste each year. If not properlydisposed of, this waste poses seriousenvironmental problems. Research onthe safe and beneficial use of poultrylitter is providing benefits to agriculturalinterests and to the public in northwestLouisiana.

With the recent return of cottonproduction to central Louisiana, cottonresearch at the Dean Lee ResearchStation near Alexandria has taken onnew life. It is more difficult to producecotton in this area of the state becausegrowing conditions are influenced bythe sea breeze effect of the Gulf ofMexico. Research at this locationfocuses on the interactions of weatherwith production input variables.

These four research stations areinvolved either directly orcollaboratively with LSU AgCenterdepartments, including agriculturaleconomics, agronomy, entomology,plant pathology and crop physiology,and other research organizations.Louisiana Cooperative ExtensionService faculty are also located in northLouisiana at the Scott Research andExtension Center in Winnsboro becauseof the concentration of the crop innortheast Louisiana.

Cotton Breeding ContinuesImproving the genetics of cotton

varieties to make them more suitablefor Louisiana conditions has been along-term commitment of the AgCenter.The cotton breeding program in Louisi-ana was one of the first such researchefforts established at a land-grantuniversity, dating back to the 1920s.

Because cotton is a tropical peren-nial species, it requires considerablegenetic manipulation to develop into aproductive annual crop for a temperateenvironment. Breeding new varieties,however, involves much more thanadapting cotton types to the environ-ment. Cotton is unique in that accept-able fiber quality, and not only yieldingability, must be bred into varieties. Fiberquality is composed of several distinctgenetically complex properties, each ofwhich must be separately bred andselected for. Development of pest-resistant plants that can overcomeinfestations of insects and nematodesto minimize use of pesticides also isimportant. The Louisiana breedingprogram has used unique plant traitssuch as leaf shape and color, bract shapeand nectar-producing inhibition todiscourage insect pests. The only currentcotton varieties for the South resistant toroot-knot nematode were developed inthe LAES cotton breeding program. The

Donald J. Boquet and B. Rogers Leonard, bothProfessors, Macon Ridge Research Station,Winnsboro, La. Donald J. Boquet B. Rogers Leonard

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contributions of the LAES cottonbreeding program are reported in thisissue. See page 13.

Best Management PracticesHelp with Profits

Historically, cotton in the Mid-South has been monoculture and grownas a summer annual crop in fields thatwere intensively tilled. Fields were leftfallow in winter, which, because of ourwet climate, exposed the soil to poten-tial runoff losses of sediment andnutrients. This runoff can contributeto nonpoint-source pollution of surfacewater bodies.

Since 1991, the AgCenter, NaturalResources Conservation Service,Louisiana Farm Bureau and otherorganizations have cooperated todevelop management practices thatprotect the soil and minimize fieldrunoff. Agricultural practices designedto reduce runoff from agricultural landare referred to as best managementpractices (BMPs). These BMPs had tobe implemented without compromisingthe long-term productivity or profitabil-ity of farms.

The development of agronomicBMPs that improve crop productivitywhile also protecting water quality hasbeen the focus of several projects. Onthe highly erodible land of the MaconRidge area, research has proved thebenefits of using reduced tillage andwinter cover crops to protect the land.Soil loss from research plots plantedusing the BMPs of winter cover cropsof wheat or hairy vetch and no-tillagepractices has been negligible, while soilloss from plots without cover crops andconventionally tilled exceeded seventons per acre per year.

In addition to the environmentalbenefits, winter cover crops and no-tillBMPs increased cotton yield anddecreased production costs. Thesepractices are called productive BMPsbecause they protect water quality, but,equally important, the research showsthey more than pay for themselves inincreased yields and cost savings.Therefore, the implementation of theseBMPs on individual farms to ensure thedesired societal benefits of clean watercan be done without adverse effects onfarm profitability. The benefits of BMPsare discussed in this issue beginning onpage 32.

In other BMP research at the RedRiver Research Station near BossierCity, researchers are examining ways to

beneficially use waste from Louisiana’slargest animal industry in an environ-mentally safe manner. Poultry litterapplied to cotton fields in conjunctionwith conservation tillage producedhigher yields than cotton grown usingthe conventional methods that did notemploy BMPs. Soil organic mattercontent and the nutrient status of the soilwere also improved. As an added bonus,inorganic fertilizer nitrogen was notneeded where poultry litter was applied.This research demonstrates that produc-tion of a potentially harmful waste canbe turned into a BMP by safely return-ing the waste to agricultural rowcropland in a manner that improvesthe soil and cotton yields.

Defoliation Timing CriticalOnce bolls are mature, a critical

operation remains before the cotton canbe picked. Harvest aids must be appliedto remove leaves and temporarily haltplant growth to allow picking of theseedcotton. This process of defoliationimproves the efficiency of harvestingand preserves fiber quality. Propertiming is essential to avoid yieldreductions from too-early terminationof growth and too-late termination thatcompromises harvest timing and fiberquality. Determination of the optimaldefoliation timing has been described asmore of an art than science. The variousmethods for determining the proper timeof defoliation to achieve a balancebetween yield and quality concernsare discussed on page 28.

Irrigation SchedulingLouisiana’s highly productive soils

have one major limiting factor—erraticsummer rainfall. Supplemental irriga-tion is essential for profitable cottonproduction in most years on some soils(loess) and for insurance againstexceptionally dry years on other soiltypes. In most of Louisiana, water fromwells or surface sources is readilyavailable for irrigation. Determining theneed for and scheduling irrigation is notstraightforward, however, because dryweather is sometimes followed byrainfall. When this happens, any benefitsof the apparent needed irrigation arenegated and, in fact, irrigation maycause a yield loss. Some of the waysto avoid these irrigation problems andoptimize the benefits of irrigation arebeing evaluated at the NortheastResearch Station.

Integrated Pest ManagementMore than most other crops, cotton

requires protection from insects,nematodes and diseases. Until the lastdecade, more pounds of pesticide peracre were used on cotton in a given yearthan on any other agronomic crop. Theintegrated pest management (IPM)system has moderated pesticide use oncotton. In recent years, highly target-specific pesticides that can be used atlow dosages (ounces rather pounds peracre) have become available. Geneticengineering has produced cotton plantsresistant to insect pests and tolerant toapplications of selected herbicides. Inaddition, a better understanding ofcotton pest biology and interactions inagricultural environments has improvedthe ability of producers to adapt cropprotection solutions to each individualneed. The ultimate goal of LSUAgCenter scientists with responsibilitiesfor improving cotton IPM is to developpractical crop protection solutions intoexisting production systems withminimal effects on nontarget organismsand the environment.

Weed Management ChangesWeed management in cotton has

changed considerably in the past decade.The adoption of conservation tillagepractices has reduced the emphasis ontillage as weed control and increasedreliance on herbicides. Producers areusing pre-plant herbicide applications,called burndowns, to establish weed-freeseedbeds. Novel herbicides used in post-emergence, over-top applications havebeen successful in controlling broadleafweed problems such as morninggloryand pigweed without injury to cottonplants. Producer acceptance of herbi-cide-tolerant cotton has simplified weedmanagement in cotton by reducing theemphasis on pre-plant, soil-applied andpost-directed herbicides. In 2001 and2002, herbicide-tolerant cotton varietiesaccounted for more than 75 percent and55 percent, respectively, of the totalplanted acreage in Louisiana. Extensiveresearch programs in the AgCenter havedefined cotton plant and pesticidecharacteristics that enhance the differen-tial selectivity between crop safety andweed control.

Insect ManagementGoes Hi-Tech

The evolution of cotton insect pestmanagement strategies has followed atrend similar to that of weed manage-


ment. Research on highly selectivenovel insecticides, environmentallyfriendly insecticide delivery systems,transgenic insect-resistant cottonvarieties and insect ecology has pro-vided information to develop cost-effective alternatives to recommendedinsect pest management practices. Theeradication of the boll weevil as a cottonpest has greatly reduced the applicationfrequency of nonselective insecticides.In the absence of these treatments,which were toxic to a broad spectrum ofinsects, innocuous insects have emergedas significant pests that now are capableof limiting yield. Current researchfocuses on the development of site-specific insect management withinsecticide prescriptions. Adaptingprecision agricultural technologies tocotton insect pest management strate-gies could further reduce insecticide

inputs with economic and environmentalbenefits.

Tillage Practices AffectDisease Management

The dynamics of cotton diseasemanagement have shifted with changingtillage practices and short-seasonvarieties. Although the pathogensplaguing cotton plants have notchanged, the dynamics of cottondiseases have. Increased use of conser-vation-tillage practices has altered thesoil environment, leading to an increase

in the diversity of soil organisms. Theeffects of increased microbial interac-tions on specific plant pathogens arecomplex and not completely understood.Some pathogens may increase in thealtered environment, and others maydecrease. Research is continuing toevaluate the effects of disease patho-gens, but general uncertainty hasprompted producers to re-evaluatethe need for additional fungicides atplanting.

The impact of reduced-tillagepractices on nematode populations isalso not completely understood, butresearch is under way. The reniformnematode has emerged as the state’s No.1 nematode pest, replacing the root-knotnematode. Current research efforts aretargeting management of this pest.

The sporadic occurrence of late-season maladies has had mixed effects

on cotton development. Bronze wilt isusually associated with specific short-season cotton varieties and can reduceyields drastically. Boll dangle orvascular cavitation, in contrast, destroysmany young bolls but is associated withhigh-yielding varieties and is apparentlynot yield-limiting.

Improved TechnologySustains Cotton Industry

Innovations in technology havegreatly changed the way cotton isgrown, improving production efficiency

from pre-plant operations throughharvesting. Although no single technol-ogy can be said to have saved the cottonindustry, all of the improvements intechnology during the past 50 yearstogether have enabled the cottonindustry to survive, if not prosper.Perhaps the greatest change in technol-ogy is use of transgenic seed with insectand weed control attributes, whichtransfer the cost and the burden ontoproducers of making what used to bemid- and late-season decisions atplanting time. Despite problems andhigh cost, the use of transgenic varietiesis the most rapidly adopted technologychange in agricultural history.

The adoption of environmentallyfriendly conservation tillage practicesalso has had profound effects in revolu-tionizing cotton production practices.Although promoted for environmental

benefits, conservationtillage improvesefficiency and makesit easier and less costlyfor producers to growcotton. Likewise, largercotton pickers andmore effective harvest-ing equipment such asboll buggies andmodules have im-proved the efficiencyof harvesting cotton.The improved technol-ogy has benefitedcotton growers, but at ahigh cost. The econom-ics of technologicalinnovations for cottonproduction are dis-cussed on page 15.

The articles in thisissue are examples ofresearch and extensionefforts put forth byLSU AgCenter scien-

tists to provide solutions to problemsbeing experienced by the Louisiana andthe Mid-South cotton industry. Thesescientists are integrating their resultsinto holistic, intensive and sustainablecotton production systems. All of thecotton varieties—and agriculturalproduction systems in general—aredeveloped so that they meet the eco-nomic and environmental challengesthat face Louisiana agriculture.

Cotton “modules” now dot the landscape in cotton country during harvest. These huge white loaves arecreated by module builders that compress the cotton, making the transport to the gin a more efficientprocess. Before module builders, farmers used trailers to haul cotton from the fields to the gin. This was aslow process that delayed harvest and resulted in reduced yield and fiber quality.

Photo by John Wozniak


eospatial tools offer greatpromise of increasing profitability ofcotton production. These tools, however,must be adapted to the specific agro-nomic and plant protection needs ofcotton production and made available ina user-friendly format that can be easilytransferred to producers, commercialpesticide applicators and agriculturalconsultants.

In 2002, a multi-disciplinary teamincluding LSU AgCenter scientistsinitiated a project to develop spatiallyvariable pesticide applications based onremote sensing to improve the effi-ciency and profitability of cottonproduction. The objectives of the studyare: 1) to correlate arthropod densitieswith field growth patterns, 2) to applyspatially variable pesticide applications

to targeted zones in a field,3) to perform economiccomparisons of precisionfarming techniques toconventional plant protec-tion strategies and 4) todevelop and disseminateeducational programs onthe efficiency and valueof precision agriculturetechniques.

The study is beingconducted at HardwickPlanting Co. near Somerset,La. Images are gathered withfixed wing aircraft flown at12,000 feet. These multi-spectral images are geo-

referenced and used to create a Normal-ized Difference Vegetation Index(NDVI) of the study site, which pro-vides an estimate of plant vigor.

To correlate arthropod densitieswith multi-spectral images, test fields(300 to 450 acres total) were sectionedinto one-acre grids. Five randomlyselected sites are then sampled for thepredominate arthropods in each one-acregrid. Arthropod density data are thencorrelated with multi-spectral imagedata.

Ralph D. Bagwell, Associate Professor, and B.Rogers Leonard, Professor, Macon Ridge ResearchStation, Winnsboro, La.; Jay W. Hardwick,Operator, Hardwick Planting Co., Somerset, La.;Edwards Barham, Aerial Applicator, BarhamBrothers Aviation, Oak Ridge, La.; Dale Magoun,Head, Department of Mathematics, ComputerScience and Physics, University of Louisiana atMonroe, Monroe, La.; Randy Price, AssistantProfessor, Department of Biological and Agricul-tural Engineering, LSU AgCenter, Baton Rouge,La.; Robert G. Downer, Associate Professor,Department of Experimental Statistics, LSUAgCenter, Baton Rouge, La.; and Kenneth W.Paxton, Professor, Department of AgriculturalEconomics, LSU AgCenter, Baton Rouge, La.

LSU AgCenter scientists are experimenting with technology that will make it possible for aerial applicators to sprayprecisely what’s needed over every square foot of a field. Their aim is to make this technology usable and affordable for farmers.

Photos by John Wozniak

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Precision Agriculture AidsCotton Pest ManagementPrecision Agriculture AidsCotton Pest Management

Ralph Bagwell, above, and Roger Leonard are the leadLSU AgCenter scientists in this precision agricultureproject.


To determine economic value ofthis technology, insecticide applicationsare compared with traditional broadcastapplications when arthropod densitiesreach the treatment threshold. Areasselected for variable rates are deter-mined by multi-spectral imaging.Generally, insecticides are applied toareas indicating high plant vigor (60percent to 80 percent of the field) andnot applied to areas with the lowestplant vigor. Four paired cotton fields (75to 120 acres) are treated with either thevariable or traditional sprays. Lint yieldsand production costs are then comparedfor the two treatments.

The third evalua-tion looks at yieldhistory to determineareas where pesticideapplications are rarelyjustified. Geo-refer-enced historical yieldsare identified andpesticide exclusionzones are created inlow-yielding areas.Three to four replicatesof these treatments arecompared withtraditional whole-fieldsprays. Lint yields andproduction costs arethen compared.

The final evaluation is a replicatedcomparison of spatially variabledefoliation treatments with traditionalblanket defoliation treatments. NDVIimages are used to develop multiple-ratedefoliation treatments. Defoliant ratesare varied by changing the outputvolume of the spray equipment. Treat-ments are replicated three to four timesand are sufficient in size that one,preferably two, modules can be madefrom each plot. Lint yields, productioncosts and lint quality factors are thencompared.

These research results will providethe basis for integrating geospatial

technologies into the current cottonproduction system. A demonstrationprogram will be developed for produc-ers, pesticide applicators and agricul-tural consultants on the efficiency andvalue of precision agriculture in cottonIPM.

The results of this project willcontribute the necessary informationto integrate geospatial technologies intocurrent IPM systems. The days of the“pesticide treadmill” with its disastrousresults of pest resurgence, secondarypest outbreaks and environment con-tamination in cotton production systemsmay be eliminated if a base of informa-tion can be developed to support theappropriate development of thesetechnologies.

Photos by John Wozniak

The computer in the cockpit controls whenthe sprayer nozzles (below) are turned onand off.

Shot from 12,000 feet, this aerial photo indicates throughcolor where there is plant vigor. This can help determinewhere insect pests are.


SU AgCenter scientists havelaunched a project to explore the useof geographical information system(GIS) and global positioning system(GPS) technologies to managenematodes that affect cotton produc-tion in Louisiana soils. GPS-basedequipment makes it possible tomeasure soil electrical conductivityfor texture mapping, to developtopographic maps and to applyvariable rate treatments. Currently,nematode treatments are usuallyapplied uniformly across fields,often resulting in considerable over-application.

The southern root-knot nematodeis a severe nematode pest in Louisianasoils. Crop rotation, root-knot nema-tode resistant varieties and pesticidesare required to manage the pest.Agronomic options of crop rotationand use of resistant varieties areusually limited. When chemicaltreatments are selected as a principalmeans of control, costs can exceed$30 per acre for high infestations ofroot-knot nematodes.

In 2000-2001, preliminary datawere collected from the Gin Ridgefield at the LSU AgCenter’s NortheastResearch Station near St. Joseph, La.,which was highly infested with root-knot nematode. Surveys of the GinRidge field included soil electricalconductivity readings measured witha Veris mapping cart (see photo thispage), topography data collected usingprecision laser equipment and soil

L

Eugene “Gene” Burris, Professor, and RichardCostello, Post Doctoral Researcher, both at theNortheast Research Station, St. Joseph, La.;Boyd Padgett, Professor, Macon RidgeResearch Station, Winnsboro, La.; CharlesOverstreet, Professor, and Maurice Wolcott,Research Associate, Department of PlantPathology, LSU AgCenter, Baton Rouge, La.

With a Verismapping cart,scientists canmeasure the

electricalconductivity of

soils, whichcorrelates with

soil texture.

Eugene “Gene” Burris, Richard Costello, Boyd Padgett,Charles Overstreet and Maurice Wolcott

Figure 1. Overlaying a boundary using the LSU GIS database and the SSToolboxprogram identifies a 78.3-acre field, called the Gin Ridge field, on the NortheastResearch Station at St. Joseph.

Photo by Mark Claesgens


Figure 3. A grid sample overlay of the nematode population densities indicatesthat high or very high nematode counts were found only on the ridge areas ofthe field that also correspond to the lighter soil textures.

Figure 2. Comparisons of electrical conductivity surface data (EC) andtopographic elevation maps facilitate soil texture mapping, which is used todetermine rate of application.

samples taken on a 1-acre grid. Fromthese samples, soil texture and nema-tode population densities were deter-mined. All applications incorporated adifferential global positioning systemto ensure accurate data collection.These data were used to segregate thefield into zones characterized bydifferences in soil texture and to showthe relationship of plant parasiticnematode populations within differentsoil zones.

Information collected was ana-lyzed using SSToolbox, a computerprogram used with GIS technology. InFigure 1, the 78.3-acre Gin Ridge fieldboundary is outlined and overlaid onan aerial photo. In Figure 2, thecomparisons of field zones are shownfor the Veris electrical conductivitydata and the elevation data. Severaldifferent soil textures occur in the78.3-acre field—Commerce silt loam,Bruin silt loam, Mhoon silty clay loamand Sharkey clay. In Figure 3, theresults of nematode samples collectedon a 1-acre grid are overlaid on theelevation map. These graphic depic-tions indicate that the root-knotnematode infests only a portion of thefield. This has allowed the scientists todevelop variable rate prescriptions forpesticide treatment, reducing the needfor nematicide by 60 percent.

With the help of a grant from theU.S. Environmental ProtectionAgency, the LSU AgCenter researchteam will expand its efforts to providebetter knowledge of plant parasiticnematode distributions and densities.The team will evaluate several fieldswith a history of nematodes anddevelop Veris information, topographydata guidance systems and variablerate applications. The objectives of theresearch include enhanced ability tosample plant parasitic nematodes andcreation of GIS/GPS-based strategiesthat will be user-friendly so producerscan more effectively manage plantparasitic nematode infestations.

Louisiana is one of 14 states where 98 percent of U.S.cotton is grown. The others are: Alabama, Arkansas,Arizona, California, Georgia, Mississippi, Missouri, NewMexico, North Carolina, Oklahoma, South Carolina,Tennessee and Texas. The remaining 2 percent is grown inKansas, Florida and Virginia.

Texas, which annually grows about 4.5 million bales ofcotton, is the leading cotton-producing state.

Historically, China is the country that produces the mostcotton.

U.S. paper currency is made up of 75 percent cotton and25 percent linen.

One bale of cotton can produce 215 pairs of jeans.

Cotton FactsCotton Facts


ystematic research in cottonbreeding and genetic improvementbegan in Louisiana when H.B. Brownjoined the staff of the Louisiana Agri-cultural Experiment Station (LAES) in1926. The objectives of the cottonimprovement and breeding programwere to increase lint yield, to producemore uniform, longer cotton fiber andto produce larger bolls. Early studies byBrown also involved investigations ofleaf shape and plant pubescence. In1936, Brown was joined by John Cotton,a U.S. Department of Agriculture cottonbreeder and geneticist who contributedto the improvement of disease resistancein LAES cotton germplasm.

When Brown retired in 1946, F.W.Self became the lead cotton breeder forLAES, and a major effort was initiatedto improve fiber and seed quality. Therelease of Stardel in 1955 represented asignificant advance in fiber strength anduniformity. Stardel Glandless was acommercial variety released in 1967;it was marketed as Rogers OB1.

M.T. Henderson served with Selfand was involved in cotton genetics andtaught many young scientists. Many ofHenderson’s students went on to have amajor impact on the cotton industry.One of these students, Jack E. Jones,was responsible for cotton breeding andvariety development at the LAES from1950 to 1990. Jones’ research focusedon the Fusarium wilt-nematode diseasecomplex, reniform nematodes, keyinsect pests (bollworm-budworm, bollweevils, plant bugs) and how open-canopy traits affected boll rot, earliness,insects and yield. These studies resultedin the release of three varieties withunique leaf shape: Gumbo, an okra leaf(narrow leaf) variety released in 1976;Pronto, a super okra leaf variety releasedin 1976; and Gumbo 500, an improvedokra leaf variety released in 1981. From1990 to 1994, Steve Calhoun conductedthe cotton breeding and improvementprogram for the LAES. The presentbreeder, Gerald Myers, assumedresponsibility for the program in 1994.

Improving Cotton Varietiesin Louisiana

Fiber ImprovementWhile there is little direct economic

incentive for producers to sacrifice yieldfor fiber quality, cotton breeders,especially those in the public domain,are expected to be vanguards of cottonquality. Better fiber translates into betteryarn, which enables cotton to competeeffectively with synthetic fiber. There-fore, the health of the cotton industrydepends on high-quality fiber.

Three of the most important traitsfor textile operations are fiber length,strength and fineness. Although lengthis primarily determined by the plant’sgenetic makeup, stressful growing

and a low quality fabric. Immaturefibers cause more fabric imperfectionsand are difficult to dye. In Louisiana,most immature fiber is produced in theuppermost fruiting sites, which are oftenlost to late-season insect pests or notharvested by once-over picking prac-tices. Since the bulk of Louisiana cottondevelops in systems promoting fibermaturity, micronaire becomes primarilya measure of fineness. Fiber fineness isalmost under complete genetic control,with environment having little effect.Unfortunately, concessions occurbetween development of low micronaireand high yield. With other factors beingequal, an increase in micronaire resultsin more pounds of lint per acre.

With cooperation of researchersfrom several disciplines and supportfrom producer organizations, greatstrides have been made in improvingfiber quality and enhancing yield.Researchers at the Pee Dee ExperimentStation in South Carolina were some ofthe first to improve yield and fiber traitssimultaneously. The Texas A&M cottonbreeding program at Lubbock, withsupport from Plains Cotton Growers,Inc., is releasing upland cottongermplasm with 35 percent better fiberlength and 50 percent better strengththan regional standards, with little tono trade-off in yield potential.

An important aspect of the cottonimprovement effort has been the CottonFiber Testing Laboratory located on theLSU campus in Baton Rouge. The fiberlab, operated for many years by WilburAguillard and more recently by IvanDickson, was recently equipped with amodern Uster High Volume Instrumentfor comprehensive fiber evaluation.This service is invaluable in providinginformation on the fiber quality.

W. David Caldwell, Professor, Red River ResearchStation, Bossier City, La.; Gerald O. Myers,Associate Professor, Department of Agronomy,LSU AgCenter, Baton Rouge, La.; Steve Hague,former Assistant Professor and now with BayerCotton Seed in Leland, Miss.; and James A.Hayes, Research Associate, Red River ResearchStation, Bossier City, La.

S

conditions can shorten fiber. Frequently,breeding lines with long fiber have lowlint-to-seed ratios that can contribute tolow yield. Fortunately, selectionmethods are being perfected to circum-vent this conundrum.

Fiber strength is governed largelyby genetics, with some loss attributed tosevere weathering between boll openingand harvest, extreme plant stress duringfiber development or harsh ginningpractices. Fiber strength usually trans-lates directly into yarn strength. This hasbecome increasingly important inmodern textile mills because machineryoperates at escalating speeds with littleeconomic cushion for work stoppagescaused by breaks in the spinning andweaving processes.

Micronaire is an indicator of bothfineness and maturity. Coarse fiberresults in a lower fiber per thread count

Better fiber translatesinto better yarn, whichenables cotton tocompete effectively withsynthetic fiber. Therefore,the health of the cottonindustry depends on high-quality fiber.

W. David Caldwell, Gerald O. Myers, Steve Hague and James A. Hayes


Principal genetic resources thatenhance fiber traits are from Acalabreeding lines and naturally occurringvariation within adapted varieties. Acalalines are primarily grown in the westernUnited States and Australia but havebeen moderately successful in Louisi-ana. Most cotton producers rememberDeltapine 90, which had an Acalabackground. More recently, several linesfrom Australia have been commerciallyintroduced with extensive geneticcontributions from Acala lines. Cottonvarieties are not entirely homogeneouspopulations and possess variation formost traits. Unfortunately, finding thesetraits can be likened to the proverbialneedle in the haystack. Breeders mayclosely examine tens of thousands ofplants before finding a single off-typeimprovement.

Cotton Breeding ProgramThe Cotton Breeding and Genetics

Program of the LSU AgCenter seeks tobuild on its successes, which were

significant in the 1990s. These includethe release of several cotton varietiesdeveloped by Jack Jones—StonevilleLA 887, Paymaster (Hartz) 1215, 1220,1244 and 1560. Transgenic versions ofthese varieties have also been marketed.Notable among these is Paymaster1218BG, the most widely planted cottonvariety in the Mid-South for twoconsecutive years in a row (2001 and2002) and Stoneville ST 5599 BR (atransgenic version of LA 887), marketedfor the first time in 2003. Both have theBollgard gene for insect resistance andthe Roundup Ready gene for herbicideresistance. Royalties from the sale ofseed support the LSU AgCenter breed-ing program and other related research.Additional research was conducted intonatural plant traits that confer resistanceto insect pests and stresses, the identifi-cation of resistance to nematodes andthe genetic inheritance of numeroustraits. Germplasm from this researchwas developed and released for use byother cotton breeders.

Since 1994, the Cotton Breedingand Genetics Program has been directedby Gerald Myers and retains thehistorical focus of developing cottongermplasm and varieties with high yieldpotential, increased resistance to pestsand superior fiber quality specificallyadapted to Louisiana and the Mid-South.Research trials are undertaken incollaboration with LSU AgCenterscientists and research stations through-out the state, as well as cotton breedersacross the United States.

The breeding program is based ona pedigree system. Recent focus areasbeyond that of high and stable yield andsuperior fiber quality include developinggermplasm with tolerance to both root-knot and reniform nematodes (highlydestructive soil pests of cotton widelyscattered in the state), developinggermplasm with resistance to Heliothispests and developing varieties with theokra leaf shape.

Research projects recently con-cluded have shown that the insertionof transgenes for insect and herbicideresistance has made subtle changes inother plant characteristics and hasidentified new sources of resistanceto the root-knot nematode. With recentgrants from Cotton Incorporated and theLouisiana Cotton State Support Com-mittee, research projects on improvingthe efficiency of breeding for betteryield and fiber quality and on character-izing newly acquired cotton germplasmfrom Uzbekistan have begun.

Beginning in 1995, the programhas been conducting research in cottonmolecular genetics and biotechnology.Support from the Louisiana EducationalQuality Support Fund helped establishthis aspect of the program, which hastwo focus areas: molecular mapping ofgenes for yield components and fiberquality and on cotton transformation. Arecent paper reports on the identificationof a marker associated with increasedyield in cotton. This DNA marker isbeing further investigated for its use inmarker-assisted selection of increasingcotton yield. Efforts to develop thecapability to genetically transformcotton are under way. Regeneratedplants have been developed and researchto increase the efficiency of the processis being conducted. This research iscomplementary to the conventionalbreeding program, and it is through acombination of the two that progressby the Cotton Breeding and GeneticsProgram can be measured.

Donald J. Boquet and B. Rogers Leonard, both Professors, Macon Ridge ResearchStation, Winnsboro, La.; and W. David Caldwell, Professor, Red River Research Station,Bossier City, La.

Farmers have been growing cotton since 4,000 B.C. in India. In the NewWorld, cotton production goes back well before Columbus landed in the Bahamasin 1492. He took cotton back to Spain to prove he had circled the world andreached India. Until the 18th century, England was the center of the Europeanwool clothing industry but, once introduced, cotton quickly became the preferredfiber because of its advantages over wool for summer clothing. In the 18th century,the English wool industry successfully sponsored laws to ban cotton, eventuallyto no avail. Because cotton was a tropical crop that could not be grown in Europe,these countries used their colonial system to support the development ofextensive cotton production in many temperate and tropical areas of the world.

Cultivation of cotton in Louisiana was reported as early as 1729. At that time,cotton fiber was used in home spinning and weaving. It was not until the inventionof the cotton gin in 1793 by Eli Whitney that cotton was produced in Louisianaas a cash crop, primarily for export to Europe. By 1860, the United States wasproducing 75 percent of the world’s cotton. Between 1870 and 1920, cotton wasgrown on as many as 48 million acres and was the only major cash crop in theSouth. This quickly changed with the arrival of the boll weevil from Mexico in the1890s. The boll weevil became the most devastating insect in the history ofagriculture, forcing thousands of farmers out of the cotton business and servingas the primary impetus for the diversification of Southern agriculture, thedevelopment of the chemical insecticide industry and the aerial pesticide applica-tion industry. When the cotton picker was invented in 1927, each picker couldreplace more than 100 hand laborers. The loss of these jobs began the processthat would eventually lead to large permanent migrations of rural Southerners tothe cities in search for jobs.

Cotton History


ur nation’s cotton production hasundergone tremendous adjustments inthe past 50 years fueled by the forces oftechnical change. One prime indicator ofthe magnitude of changes is yield peracre. At the national level, per acrecotton yields have increased more than64 percent since the mid 1950s. At thesame time, area devoted to cottonproduction has decreased 17 percent.The increased yield per acre can belargely attributed to the technologiesembodied in new pesticide chemistries,novel pest management systems,efficient irrigation and cultivation, andimproved cotton varieties.

In Louisiana, per acre cotton yieldsincreased more than 42 percent duringthe last 50 years. While Louisianafollowed national trends in terms ofyield per acre, the same was not true ofacres planted to cotton. In the last threeyears, cotton producers planted about 14percent more cotton, on average, thanthey did in the mid 1950s.

Another indicator of the magnitudeof changes is change in efficiency madepossible through technological innova-tions. These innovations have generallytaken the form of substituting capital forlabor. One example of this type ofinnovation is the cotton picker. Whenoriginally introduced, the one-rowpicker replaced several workers in thecotton harvest operation. As the me-chanical picker has been improved, ithas become more efficient; the newmultiple row pickers allow one person

to harvest several times more cotton perday than was possible with the originalsingle-row machines.

Innovations adopted by cottonproducers have been driven by econom-ics. These innovations can be dividedinto two general categories—biotech-nology and other technology.

Biotechnology ChangesCotton Production

Biotechnology has only recentlybeen introduced into cotton productionon a commercial scale. This has gener-ally taken the form of insect resistanceand herbicide tolerance. The adoptionof these technologies by producers hasbeen extremely rapid. Several studieshave examined why the adoption of thistechnology has been so rapid. Generally,producers adopted the technologiesbecause they were effective and pro-vided some economic incentive foradoption. Several studies have examinedthe question of the distribution ofbenefits from the adoption of suchtechnology. Results of these studiesgenerally found that producers whoadopt the technology receive the largestportion of the benefits.

Cotton varieties containing genesthat provide insect or herbicide resis-tance were first introduced commer-cially in 1996. In 1999, varietiescontaining these genes accounted formore than 50 percent of the U.S. cottonacreage. There was considerable

variation in the level of adoption ofthese varieties among cotton-producingstates. In the West, the level of adoptionwas relatively low because the targetinsect pest is not as great a threat there.The Mid-South and Southeast areas hada considerably higher level of adoption.For example, Louisiana cotton produc-ers planted more than 70 percent of theacreage in 2002 to insect- and herbicide-resistant varieties. Much of this acreagewas planted to “stacked gene” varieties,which means they included both insect-and herbicide-resistant traits.

How effective are modified variet-ies? The answer is in the comparison ofinsect damage before and after introduc-tion of the insect-resistant varieties.From 1990 to 1995, cotton producers inLouisiana experienced an average lossof 4.11 percent attributable to thebudworm/bollworm complex. From1996 to 2001, this dropped to a 2.1percent average loss. The 2.1 percentincludes data from 1996 to 1998 whereno distinction was made betweenconventional and Bt varieties. Duringthe 1999-2001 period, Bt varietiesaveraged a 0.92 percent loss attributableto the budworm/bollworm complexwhile the conventional varieties experi-

Kenneth W. Paxton, Professor, Department ofAgricultural Economics and Agribusiness, LSUAgCenter, Baton Rouge, La.

O


Economicsof Technology Use

in Cotton

Economicsof Technology Use

in Cotton

Kenneth W. PaxtonKenneth W. Paxton


enced an average loss of 2.24 percent.These data indicate that adoption of theBt varieties dramatically reduced thelosses attributable to the major insectpest of cotton in Louisiana.

Although comparable data are notavailable for the herbicide-resistantvarieties, annual enterprise budgetprojections provide one means ofcomparing the stacked gene varietiesagainst conventional varieties. Budgetprojections for 2002 show that herbicidecosts for conventional versus stackedgene cotton are about equal. However,this cost does not reflect the higher levelof management required in using

Mechanical Pickers ToPrecision Agriculture

Technological innovations have hada significant impact on cotton produc-tion, ranging from mechanical pickersto precision agriculture. The impact ofmechanical harvesters has been welldocumented. Subsequent improvementsin harvest machines have continued toincreased productivity of labor. Not onlyhave the harvest machines become moreefficient, but their efficiency has beenenhanced by introduction of the modulebuilder and more recently the bollbuggy. These innovations have signifi-

the producer, but most are environmen-tally friendly. Because these systemsmaintain a cover on the soil, erosionis reduced. Some studies have demon-strated a synergistic relationshipbetween herbicide-resistant varietiesand reduced tillage systems.

Currently, much emphasis is placedon developing technology in the area ofprecision agriculture. Innovations rangefrom automatic guidance systems tousing remotely sensed imagery tomanage crop production. Of particularinterest to Louisiana cotton producersis the technology necessary to capturecritical management information on afield, interpret the data and implementtimely management decisions. Prelimi-nary work in Louisiana and elsewhere inthis area has demonstrated the potentialof this technology to significantlyreduce insecticide costs.

Central to achieving these savingsis the ability to adequately and accu-rately describe the spatial distribution ofinsects and other pests across individualcotton fields. With information on thedistribution of the kinds and amountsof pests in the field, prescriptions can bedeveloped to manage those pests. This isdone by using variable rate technology(VRT) to apply chemicals or otherinputs to designated areas in the fieldin the precise amounts needed. Thetechnology also can be used to improvesoil fertility, drainage and irrigationefficiency. The potential for cottonfarmers to adopt this technologydepends on the same factors cited earlierfor the biotechnology innovations—profitability and effectiveness.

Most studies of precision farminghave found it to be profitable. Most ofthis work has been done with variousgrain crops because of the availabilityof yield monitors for those crops. Yieldmonitors for cotton have only recentlybecome available commercially. Recentresearch in the Southeast on precisionagriculture in cotton indicates severalpotential benefits—improved productionefficiency, reduced input use, increasedyields and higher profits.

Widespread adoption of biotechnol-ogy and precision agriculture technolo-gies holds tremendous promise ofadditional benefits. These benefits gobeyond the environmental benefits ofreduced pesticide use and extend to thepotential for reducing soil loss andcontributing to a more sustainableproduction agriculture.

LSU AgCenter Photo Archive

This is a tractor-mounted cotton picker. The photo was taken in 1947 in Tensas Parish.

herbicide-resistant varieties, whichinclude restrictions on when over-the-top herbicides can be applied. Insecti-cide costs, on the other hand, are quitedifferent between the two kinds ofvarieties, with the stacked gene varietiescosting about $15 per acre less. How-ever, the additional technology feeassociated with these varieties offsetsthis advantage. Further, the boll weevileradication program combined with thewidespread adoption of insect-resistantvarieties has changed the insect pestcomplex for cotton. While damagefrom the budworm/bollworm complexand boll weevil has been mitigated,other pests have emerged, and insecti-cide applications are required tomanage these populations.

cantly improved harvesting efficiencyand reduced costs. Further, the modulebuilder made it feasible to transportcotton longer distances. This enhancedtransport ability led to a reduction in thenumber of gins required. Having fewerbut larger gins has changed the nature ofthe ginning industry not only in Louisi-ana, but across the Cotton Belt.

Several innovations in tillageequipment have enabled producers to doa better job in soil preparation and cropcultivation. Much of the focus in tillageequipment innovation is on minimum orno-till equipment. Improvements haveencouraged adoption of reduced tillageproduction systems among cottonproducers in Louisiana and elsewhere.These systems not only reduce costs for


Resistance monitoring provides a useful tool for detectingchanges in the insecticide susceptibility of field populations ofinsect species from year to year. During the late 1980s and intothe 1990s, resistance monitoring of the tobacco budwormprovided data for establishing and modifying the tobacco bud-worm resistance management plan implemented by Arkansas,Louisiana and Mississippi. Resistance monitoring also helpsvalidate whether field control failures are the result of a truedecrease in insecticide susceptibility or whether other factorsshould be examined to determine the cause of unsatisfactorycontrol.

Development of resistance in a key cotton pest to aparticular chemical or class of chemicals can threaten theprofitability of the industry. This is especially true when otherintegrated management strategies, including alternative chemi-cals for that pest, are limited.

In the Mid-South, two of the most devastating cotton pestsare the bollworm and tobacco budworm. The pyrethroidinsecticides provided the most economical control of these twopests during the 1980s and into the 1990s. In Louisiana, pyre-throid resistance monitoring was initiated in 1986 for thetobacco budworm and in 1988 for the bollworm. Additionally,these two pests were monitored for susceptibility to a non-pyrethroid insecticide, spinosad (Tracer), beginning in 1991 forthe tobacco budworm and in 2000 for the bollworm. Spinosadrepresents a new class of chemicals called naturalytes.

Monitoring involves the collection of male moths with wirecone traps baited with an artificial sex pheromone lure. Thesetraps were located in several parishes across the cotton produc-tion regions of the state. Adult male moths collected from thesetraps were placed in glass vials treated with one of the selectedinsecticide concentrations or in nontreated control vials.Cypermethrin was one of the earliest pyrethroids used forcontrol of these two cotton pests in Louisiana. Spinosad is oneof the most recently registered insecticides for control of theseinsect pests. Mortality of the moths in both the treated andcontrol vials were determined after 24 hours of exposure.Information presented here is based on seasonal percentagesurvival of these two cotton insect pests.

Insecticide Resistance Monitoring Programsin Louisiana Cotton

Stephen Micinski, Associate Professor, Red River Research Station,Bossier City, La.; Donald R. Cook, Research Associate, Department ofEntomology, LSU AgCenter, Baton Rouge, La.; B. Rogers Leonard,Professor, and Ralph D. Bagwell, Associate Professor, Macon RidgeResearch Station, Winnsboro, La.; Eugene “Gene” Burris, NortheastResearch Station, St. Joseph, La.; and A.M. “Sandy” Stewart, AssistantProfessor, Dean Lee Research Station, Alexandria, La.

Figure 1 shows the percentage survival of the pests in thelast 15 years to cypermethrin. Bollworm survival remainedrelatively constant at a level below 10 percent from 1988 to1997. During 1998, bollworm survival reached 18 percent andwas followed by two years at 16 percent. In 2002, bollwormsurvival increased to 34 percent.

Tobacco budworm survival was more pronounced. From1994 to 1996, survival appeared to be stabilizing at 39 percentfor the tobacco budworm. However, in 1998 survival increasedto 55 percent and has remained near 60 percent for the last fouryears. By 1999, the pyrethroids were removed from the cottoninsect recommendations for control of the tobacco budwormdue to the increased likelihood of field failures due to pyrethroidresistance.

Tobacco budworm and bollworm survival to spinosad isshown in Figure 2. Tobacco budworm survival in 2002 wasextremely high, reaching 52 percent. In 2001, survival was only11 percent, which was similar to survival observed during theearly 1990s. Bollworm survival followed a similar pattern. Ingeneral, results were similar to those for tobacco budworm,although overall survival was much lower. The results withspinosad are highly variable and indicate the need to continue tomonitor bollworm and tobacco budworm susceptibility tospinosad. At this time, spinosad has never been implicated in anyfield failures.

Resistance monitoring continues to be an important tool inmonitoring the susceptibility of insect populations in the field tovarious insecticide classes. Monitoring allows entomologists tofollow long-term trends in insect susceptibility. It also providesvaluable information in determining the possible causes ofinsecticide field failures when they occur.

Figure 2. Percent seasonal survival of bollwormand tobacco budworm exposed to spinosad.

Figure 1. Percent seasonal survival of bollworm and tobaccobudworm exposed to cypermethrin.

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Tobacco BudwormBollworm



Figure 3. Penetration of bolls by stink bugs causesdiscolored, yellowed lint.

he abundance of stink bugs, including southern greenstink bug, brown stink bug (Figure 1) and green stink bug, hasincreased in Mid-South and Southeastern cotton-producingstates in the last six years. Stink bugs have become morecommon cotton pests because of a number of changes inLouisiana’s agricultural environment that have made crop andnoncrop hosts available year-round. These include widespreadadoption of conservation tillage, crop rotation and conserva-

Melissa M. Willrich, Graduate Assistant, and B. Rogers Leonard, Professor,Department of Entomology, LSU AgCenter, Baton Rouge, La.

Figure 2. Young bolls, less than 12 days after opening, damaged by stinkbugs have a high probability of dropping off (abscising) from the plant.

T

Figure 1. The brown stink bug is one of the insects that hasincreased in numbers in the Mid-South and Southeastern cotton-producing states in the last six years.

Photos by Melissa Willrich

tion and wetland reserve programs. In addition, eradicationof the boll weevil and use of Bollgard cotton, which containsresistance to caterpillar pests, have both resulted in less useof broad-spectrum insecticides, which has turned pests onceconsidered secondary, such as stink bugs, into significantinsect problems. Mild winters also contribute to proliferationof stink bugs.

Stink bugs may be found in cotton fields from seedlingemergence until harvest, but they generally prefer to feed onthose parts of the plant that produce seed. Economic injury tocotton plants usually begins during boll (the fruit containingdeveloping seed) formation. Young bolls, less than12 daysafter opening (anthesis), damaged by stink bugs have ahigh probability of dropping off (abscising) from the plant(Figure 2).

Older bolls, more than 12 days after opening, when fedupon by stink bugs, will remain on the plant. Direct injury toseed and lint can affect ultimate yield and quality until thebolls have been opened at least 20 days. Penetration of bollsby stink bugs causes discolored, yellowed lint (Figure 3).

Injured bolls may display feeding symptoms on theexocarp (exterior boll wall) and internally on the endocarp(interior boll wall), seed and lint. Indications of feeding on theexocarp may be best described as dark, circular indentationson the boll wall. These symptoms are difficult to identify andsimilar injury may be caused by tarnished plant bugs. Injuryobserved in bolls approximately 12 days after anthesis shouldbe attributed to stink bugs because the tarnished plant bug,another cotton pest, does not have the ability to penetrate bollsof this age or older.


Melissa M. Willrich and

Stink Bug Damage Increases Stink Bug Damage Increases


Dark feeding punctures or wart-like cellular growths arefound on the internal carpel wall (Figure 4). This symptomcan be visible on carpel walls within 72 hours of feeding. Oneor all carpels within a boll may be injured, and it is notuncommon to observe internal injury without signs of externalinjury.

In addition to internal warts and external punctures, stinkbug damage to cotton bolls may be exhibited in other ways. Atharvest, fields that have sustained stink bug infestations havebeen associated with “hard locked” bolls (Figure 5). Hard lock

Photos by Melissa Willrich

Figure 4. Dark feeding punctures or wart-likecellular growths are found on the internal carpelwall. This symptom can be visible on carpel wallswithin 72 hours of feeding.

Figure 5. Bolls that become “hard-locked” contribute little to yield becausethey are more difficult to harvest. Stink bug infestations can cause hard lock.

is a physiological condition that can be caused by pathogens,insects or adverse weather. Hard lock symptoms include bollsthat partially open and lint that fails to fluff. These bollsusually contribute little to final yield because they are difficultto harvest with mechanical pickers.

Finally, germination rates for seed may be reduced inbolls previously punctured by stink bugs.

Producers and crop managers should become familiarwith cotton boll injury symptoms caused by stink bugs. TheLouisiana Cooperative Extension Service recommendsinsecticide treatments be initiated against stink bugs at onebug per 6 row-feet or when 20 percent of quarter-sized bolls(12-16 days after anthesis) exhibit internal injury symptomson lint, seed or endocarp. Sampling bolls is the most reliablepredictor of a stink bug infestation in cotton because of thispest’s extreme mobility and the cumbersome task of estimat-ing insect densities in late-season cotton.


B. Rogers Leonard

Cotton Insect Control, $0.75 (or on-line)Cotton Tillage Systems for Energy Reduction - Cotton

Stand Establishment, freeCotton Tillage Systems for Energy Reduction - Tillage

Equipment, freeCutworms in Cotton, freeManaging Glyphosate-Tolerant Cotton, $2 (or on-line)Producing Early-Maturing Cotton for Management of

Insecticide Resistance, free Tarnished Plant Bugs in Cotton (on-line only)

Aphids on Cotton, freeArmyworms in Cotton, freeConservation Tillage Systems for Energy Reduction -

Preplant Weed Control in Cotton, $0.50Controlling Weeds in Cotton, 32 pages, $1 (or on-line)Cotton Fertilization, free

The following publications are available at your localLSU AgCenter parish extension office or by going towww.lsuagcenter.com and ordering on-line.

Learn more about cottonLearn more about cotton

in Louisiana Cotton in Louisiana Cotton


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he tarnished plant bug has always caused problems incotton, but in recent years the problems have escalated. Datafrom 1990 to 1995, before the advent of transgenic Bt cotton,put the cost per acre to control the tarnished plant bug at $3.19compared to $12.02 from 1996 to 2002, after Bt cotton wasintroduced. The total loss in cotton because of the tarnishedplant bug was 0.41 percent from 1990 to 1995 compared to1.07 percent from 1996 to 2002.

Successful boll weevil eradication and the adoption of Btcotton, while reducing the need for insecticide applications tocontrol the boll weevil and tobacco budworm, provided anopportunity for tarnished plant bugs to flourish. Resistanceto insecticides such as the pyrethroids, organophosphates andcarbamates has contributed to control problems. Resistance tothese insecticides increases during the cotton-growing season.

Not only do these factors contribute to higher numbers oftarnished plant bugs, but the broad range of crops and wildhosts that this pest can use for survival is huge. The tarnishedplant bug is reported to have a host range of about 390 speciesof plants, giving it the broadest feeding niche of any of thearthropod pests. In the Delta, research has indicated 169 hostsrepresenting 36 families of plants. These hosts often live nextto cotton. The seasonal flowering patterns of these speciesgive the plant bug a consistent habitat from late winter thoughspring.

U.S. Department of Agriculture researchers have shown a46 percent reduction in tarnished plant bugs in cotton fields inareas where wild hosts have been controlled. Research alsohas indicated a significant economic return on investment, ofup to $10, in areas where wild hosts were controlled withherbicide applications.

LSU AgCenter researchers conducted an experiment inTensas Parish to evaluate the potential of reducing tarnishedplant bugs by managing weed hosts in field border areasadjacent to cotton fields before planting cotton. Each experi-mental area encompassed about 620 acres in 2000, 1,200 acresin 2001, and 1,700 acres in 2002. One test area in each yearwas treated with herbicide to control broadleaf weeds in fieldborders and ditches close to cotton fields.

Herbicide applications were initiated February 23, 2000,and March 19, 2001. Strike 3, a combination of 2,4-D,mecoprop and dicamba, was applied at 2 quarts per acre tokill broadleaf weeds. The weed density and species data weretaken before the herbicide treatments and three to four weekspost treatment. Tarnished plant bug adults and nymphs werecollected within each area using a standard 15-inch sweep net.Field border sampling was initiated in February beforeherbicide treatments, and sweep net data from the fieldborders were collected weekly continuing through the first

week of June. Up to 500 sweeps were made in randomlyselected cotton fields beginning in mid June through the endof July.

Throughout this study, tarnished plant bug numbers wereconsiderably lower in the areas in which the broadleaf hostshad been removed. For the most part, populations followed asimilar cyclic pattern each year. In each year there weredefinite peaks, although the peaks occurred on different dates.In general, tarnished plant bug adults began to increase inearly to mid April and nymphs in mid to late April.

In 2000, differences in the number of tarnished plant bugscaught in field borders were higher from early to mid Aprilthroughout May. Adult numbers in the treated area did not

Richard Costello, Post Doctoral Researcher, Northeast Research Station, St.Joseph, La.; Eugene Burris, Professor, Northeast Research Station, St.Joseph, La.; Gordon Snodgrass and William Scott, both Research Entomolo-gists, USDA-ARS, Stoneville, Miss.

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The average number of tarnished plant bug nymphs capturedfrom nontreated field borders also varied widely from year to year.But the numbers captured from treated borders stayed relativelyconstant in 2000, 2001 and 2002.

The average number of tarnished plant bug adults captured fromnontreated field borders varied widely from year to year. But thenumbers captured from treated borders stayed about the same in2000, 2001 and 2002.

Richard Costello, Eugene Burris, Gordon Snodgrass and William Scott

Tarnished Plant Bug Problemsand Weed Host ControlTarnished Plant Bug Problemsand Weed Host Control


Tarnished plant bugs, which have historically been amid-season pest of cotton, are now becoming a sporadic pestduring seedling development. This is happening as agriculturalconditions are changing, making it possible for more tarnishedplant bugs to survive. These changes include more plant hostsbecause of more acres going into conservation reserveprograms and an increase in conservation tillage. Anothercontributing factor is less use of insecticides because of bollweevil eradication and the increasing use of insect-resistantvarieties.

Injury symptoms resulting from tarnished plant bug feed-ing during seedling development are similar to some symp-toms resulting from thrips feeding. At-planting insecticidesused to control thrips include seed treatments or application(granules and liquids) in the seed furrow at the time of planting.

Several at-planting insecticides recommended for thripscontrol were evaluated against tarnished plant bugs in 2001.The insecticide treatments included Cruiser 5FS, Gaucho480FS, Orthene 80S and Temik 15G. Tarnished plant bugadults were caged on cotton seedlings from seven days afteremergence until 26 days after emergence. Plants were infestedat two- to three-day intervals, and mortality was determined48 hours after each infestation.

Orthene and Gaucho resulted in 2.5 percent and 18.4percent mortality of tarnished plant bug adults at seven days

Donald R. Cook, Research Associate, Department of Entomology, LSUAgCenter, Baton Rouge, La.; Eugene “Gene” Burris, Associate Professor,and B. Rogers Leonard, Professor, Northeast Research Station,Winnsboro, La.

after emergence, respectively, and mortality declined to near0 by 26 days after emergence. Cruiser produced 57.4 percenttarnished plant bug mortality seven days after emergence, andmortality declined to 13.4 percent by 26 days after emergence.Temik resulted in 76.6 percent tarnished plant bug mortalityat seven days after emergence, with mortality declining to 29.9percent by 26 days after emergence. Based on these results,Orthene and Gaucho provided little control of tarnished plantbugs at any evaluation. Cruiser provided low to moderatelevels of tarnished plant bug control, and Temik providedmoderate levels of control.

Temik and Cruiser offer some protection against tar-nished plant bugs for about three weeks, but supplementalfoliar insecticide applications may be necessary to controltarnished plant bugs during the seedling and floral bud devel-opment stages to minimize delays in crop maturity andimprove early square retention, regardless of the at-plantinginsecticide used.

The tarnished plant bug has always caused problems in cotton, butin recent years the problems have escalated.

Photo by Donald Cook

exceed two insects in 25 sweeps, and nymph numbers re-mained below one in 25 sweeps. In the nontreated area, adultnumbers began to increase in early April and peaked on May23 at 16 in 25 sweeps. In contrast, nymph numbers in thenontreated area peaked in mid April and declined throughMay.

Differences in adult tarnished plant bugs between thetreated and nontreated areas were evident by April 9 in 2001.Tarnished plant bug nymph populations did not begin to builduntil the end of April, and differences between the treated andnontreated areas were not distinguishable until May 3.Tarnished plant bug numbers in the treated area were nohigher than 1.5 insects in 25 sweeps at any rating date. In thenontreated area, numbers peaked at 10 and 11 in 25 sweepsfor adults and nymphs, respectively.

In the treated area in 2002, adult and nymph numberswere below three in 25 sweeps. Adults captured in 25 sweepspeaked at 17 on April 11 in the nontreated area. In general,nymph numbers in 2002 were lower than in the other years.The highest number of nymphs, seven in 25 sweeps, wascaught April 2.

These data indicate that destruction of wild hosts fromfield borders has the potential to reduce tarnished plant bugpopulations; however, migration of these insects from otherareas such as conservation and wetland reserve areas and cornfields, along with the inability to eliminate all wild hosts, alsocontributed to plant bug infestations. If used as part of anoverall management strategy, wild host destruction willprovide another tool to reduce insect pressure and provideeconomic value to the producer.

Effect of Soil-applied Insecticides on Tarnished Plant BugsEffect of Soil-applied Insecticides on Tarnished Plant Bugs


COMPLEXCOMPLEXCOMPLEXCOMPLEXCOMPLEX usarium wilt and the root-knot

nematode are both serious diseases ofcotton that cause substantial lossesacross the Cotton Belt. Both pathogensare common in most cotton-producingareas and often inhabit the same fields.These two pathogens often infect cottonsimultaneously, forming a complex thatincreases the incidence and severity ofFusarium wilt. The Fusarium wilt/root-knot nematode complex is one of themost widely recognized and economi-cally important disease complexes inthe world.

The symptoms caused by thecomplex are the same as those producedby the pathogens individually. Althoughcotton seedlings infected by theFusarium wilt pathogen may be killed,most symptoms appear near mid-season.The symptoms of Fusarium wilt onolder plants include wilting and chloro-sis (yellowing) followed by necrosis(brown, dead tissue) of the foliage(Figure 1) and overall stunting of theplant. The vascular system of infected

plants is discolored and readily visiblewhen the stem is cut (Figure 2). Often,infected plants mature earlier and havefewer bolls and reduced seedcottonyield. Severe infection can kill plants.Research has demonstrated that plantsmay be infected with Fusarium wilt, butthe only symptom observed is vasculardiscoloration.

Above-ground symptoms of theroot-knot nematode are not as obvious,but include stunting and yellowing orreddening of the foliage. Infected plantsappear to be suffering from nutritionaldeficiency. The most distinctivesymptom of the root-knot nematodeinfection is the formation of galls onthe roots (Figure 3).

Difficult to ManageManagement of both diseases is

difficult. Crop rotation, host resistanceand the application of nematicides areconsidered the best approaches tomanaging these diseases individuallyor together. Crop rotation is oftenrecommended to reduce the incidenceof Fusarium wilt, but the ability of thefungus to survive in the soil for long

Patrick D. Colyer, Professor, and Philip R.Vernon, Research Associate, Red River ResearchStation, Bossier City, La.

F Photos by Patrick Colyer

Figure 2. Fusarium wilt can cause stem discoloration (right).

Figure 1. This cotton plant shows symptoms of Fusarium wilt—foliar chlorosis (yellowing)and necrosis (brown, dead tissue).

This complex is one ofthe most economicallyimportant in the world.

Patrick D. Colyer and Philip R.Vernon

Louisiana Agriculture, Spring 2003 23COMPLEXCOMPLEXCOMPLEXCOMPLEXCOMPLEX

COMPLEXCOMPLEXCOMPLEXCOMPLEXCOMPLEXperiods in the absence of cotton limitsthe effectiveness of rotations. Further-more, long rotations are not economi-cally feasible for most cotton growers.Because of the ability of the nematodeto increase the incidence of wilt,rotations designed to reduce nematodepopulations may be successful inreducing the incidence of wilt.

Research has demonstrated thatroot-knot nematode-resistant soybeans,grain sorghum and peanuts are not hostsfor the root-knot nematode and are goodrotation crops for managing soilpopulations of the root-knot nematode.Most grasses and legumes used aswinter cover are also susceptible to rootknot nematode; however, since they aregrown during periods of low soiltemperatures, they are not conducive tonematode growth and infection. Becausemany weeds are hosts, fallowing is noteffective unless weeds are controlled.

Tillage Impact UnclearThe impact of tillage on the disease

complex is not clear. Tillage is thoughtto have little effect on the wilt pathogenbecause of its ability to survive in thesoil for extended periods. Tillage maydisturb the root-knot nematode andexpose it to mortality, but it may alsospread the nematode inoculum. A studywas conducted on a field with a historyof the disease complex in Bradley, Ark.,to compare reduced tillage with conven-tional tillage following a winter fallowor the winter cover crops, hairy vetchand common vetch, on the incidence and

severity of the complex. Incidence ofwilt was not affected by tillage or wintercover. The severity of root-knot nema-tode was not affected by winter coverbut was higher with reduced tillage.Although wilt was not increased in thisstudy, the increase in the severity of rootgalling by the nematode associated withreduced tillage could lead to an increasein Fusarium wilt.

NematicidesSoil fumigation, which may affect

both fungal and nematode survival inthe soil depending on the fumigant used,has successfully reduced the incidenceof wilt. Fumigation, however, isexpensive and may not be economicalfor most cotton production areas. Theability of nonfumigant nematicides, likealdicarb, that are applied in the furrow atplanting to reduce nematode populationsand root galling, has been demonstratedwidely.

In a study at the Red River Re-search Station, the effect of aldicarb(Temik 15G) on severity of the diseasecomplex in eight cotton cultivars withdifferent levels of resistance to thedisease complex was tested in 1994 and1995. Disease severity for the root-knotnematode was determined by ratinggalling on the roots and for Fusariumwilt by rating stem discoloration. Acrossall cultivars, the application of aldicarbreduced root galling and stem discolora-tion. These differences resulted inincreased seed cotton yield and lintpercentage.

Figure 3. The most distinctive symptom of the root-knot nematode infection is theformation of galls on the roots.

Host ResistanceThe use of host resistance to

manage the complex has been moder-ately successful. Although there are nowilt-immune cultivars, several commer-cial cultivars have moderate to highlevels of wilt resistance. They shouldbe planted in fields with a history ofFusarium wilt. Because the root-knotnematode increases the incidence ofwilt, and infection by the nematode canincrease the susceptibility of cultivarsthat are normally resistant, plantingcotton cultivars with resistance to thenematode will help reduce the incidenceof wilt. Regardless, wilt-resistantcultivars have a lower incidence ofwilt than susceptible cultivars in thepresence of the nematode. Unfortu-nately, only moderate resistance tothe root-knot nematode is availablein commercial cultivars.

Cultivars are evaluated for resis-tance to the disease complex annually atthe Red River Research Station in a fieldplot with uniformly high levels of theroot-knot nematode and the wiltpathogen. The results demonstratethe low level of root-knot nematoderesistance available in cotton cultivars.Only three cultivars with acceptablelevels of resistance to the complex havebeen identified: Stoneville LA 887,Paymaster 1560 and Acala Nemx.Stoneville LA 887 and Paymaster 1560were developed in Louisiana and arewell adapted to our growing conditions,but Acala Nemx was developed inCalifornia and is not adapted to the Mid-South. Based on results of these annualevaluations, it has also been determinedthat the transgenic relatives ofStoneville LA 887 and Paymaster1560 cultivars do not react like theirnontransgenic parents and are moresusceptible to the disease complex.Apparently, the resistance to thecomplex was reduced during thedevelopment of these transgenic lines.

In summary, management of theFusarium wilt/root-knot nematodecomplex remains difficult. Resistancewould be the simplest managementstrategy, but, until cultivars with higherlevels of resistance are available, tillage,crop rotation and the application ofnematicides are alternatives. Thesemethods are more effective at reducingthe infection by the root-knot nematodethan controlling the wilt pathogen. Anintegrated approach that includes all ormost of these management options is thebest strategy.

Photo by Patrick Colyer



Cotton aphids on leaves from a cotton field with high incidence of N. fresenii infection.

Robert H. Jones, former Graduate Assistant,Department of Entomology, LSU AgCenter, BatonRouge, La.; B. Rogers Leonard, Professor, andRalph D. Bagwell, Associate Professor, MaconRidge Research Station, Winnsboro, La.

he cotton aphid is a commonsecondary pest of cotton in Louisiana.Cotton aphids can infest cotton plantsfrom seedling emergence until harvestand injure plants by continuouslyfeeding on them. Injury symptoms mayinclude a downward cupping of infestedleaves, inter-veinal discoloration,compressed main stem nodes andreduced plant height. Severe cotton

aphid infestations can cause sufficientplant stress to result in square and bollshed and delay crop maturity. Inaddition, cotton aphids secrete a liquidknown as “honeydew.” The accumula-tion of “honeydew” on exposed cottonlint causes the lint to become sticky,reduces harvest efficiency and createsproblems at textile mills.

Numerous agronomic and pestmanagement practices used in cottonproduction can affect cotton aphidpopulations. Cotton aphid densities inLouisiana fields have been higher in no-till production systems. High numbersalso commonly occur as resurgentpopulations following applications ofselected insecticides for other insectpests. Natural enemies of cotton aphids

are often reduced after these applica-tions, causing cotton aphids to increaseto damaging levels. Cotton aphidpredators include lady beetles, big-eyedbugs, minute pirate bugs, lacewings andparasitic wasps.

During the past 10 years, the mostvaluable and effective non-pesticidalcontrol of cotton aphids in Louisiana hasbeen provided by a naturally occurringfungus, Neozygites fresenii Batko. Thisfungus, which spreads by airbornespores, kills cotton aphids within threedays after infection. Entire field popula-tions are reduced from peak densities tonearly non-existent levels within five to10 days after the initial infection by N.fresenii (Figure 1). These epizootics(insect epidemics) normally coincide

Fungus Helps Control

Photo by Roger Leonard

T

Robert H. Jones, B. Rogers Leonard and Ralph D. Bagwell

Fungus Helps Control


Louisiana Cotton AphidsLouisiana Cotton Aphids


Photos by Roger Leonard

“Honey-dew” stain on a cotton leaf (left) caused bycotton aphids.

Figure 1. Cotton aphid density per cotton plant terminal andpercent Neozygites fresenii infected aphids at the MaconRidge Research Station, Winnsboro, La.

with peak cotton aphid populationsduring mid-June to early July. In manyinstances, producers can delay insecti-cide applications for a few days duringthis time, allow the disease to developand not be required to provide any sup-plemental control. Usually, cotton aphidpopulations will not resurge during theremainder of the season after an epi-zootic is established, thus making N.fresenii more effective than insecticides.

N. fresenii has been a cost-effectiveand environmentally friendly pestmanagement tool for Louisiana cottonproducers. LSU AgCenter entomologistshave been cooperating with scientistsfrom the University of Arkansas tomonitor the temporal and spatial occur-rence of infected cotton aphids. Informa-tion on the status of the disease isdistributed throughout the season, givingagricultural consultants, county agentsand producers additional information toselect the appropriate integrated pestmanagement (IPM) strategy.


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uch of the land where cotton isgrown in Louisiana has been used forcotton production for decades. This hasleft the soil deficient in both nutrientsand organic matter. Some of thesedeficiencies could potentially becorrected by supplementing these soilswith organic waste from Louisiana’spoultry industry. This is the state’slargest animal industry generating tonsof organic waste that must be disposedof in an environmentally friendlymanner.

Litter produced by Louisiana’spoultry industry includes manure andbedding material. The nutrient contentof the litter varies depending upon thetype of bedding material and feed used.Generally, though, each ton of poultrylitter contains about 50 to 60 pounds ofnitrogen (N), 50 pounds of phosphorus(P) and 40 pounds of potassium (K). Theamount of nitrogen from litter that willbecome available for cotton growth

depends upon several factors includingsoil pH, temperature and moisture.However, it is generally assumed thatabout 60 percent (30 to 36 pounds perton) will become available. Therefore,at least two tons of litter are required tosupply 60 pounds of nitrogen.

To determine the potential benefitsfrom the use of poultry litter for cottonproduction in Louisiana, a study wasbegun in 1998 at the LSU AgCenter’sRed River Research Station near BossierCity, La. The study compared applica-tions of poultry litter and inorganicfertilizer in conventional and conserva-tion tillage systems. For purposes of thisstudy, conventional tillage involvedincorporating shredded cotton stalks,followed by deep tillage in the fall.Rows were bedded approximately threeweeks before planting. The conservationtillage system involved delayed seedbedpreparation and deep tillage followingthe shredding of cotton stalks in the fall,but crop residue and volunteer vegeta-tion remained on the surface until therows were bedded about three weeksbefore planting. The goal was toencourage native winter cover andmaintain at least 30 percent groundcover from harvest until three weeksbefore planting.

The studywas conducted ona Caplis very finesandy loam soil.The site consistedof approximatelyeight acres thatwere precisionsloped at 2 inchesper 100 feet withlaser land-gradingequipment.Twelve-row plots(0.25 acre) werereplicated fourtimes. Treatmentsconsisted ofconventionallytilled and conser-vation plots thatreceived either 60pounds of nitrogen

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1636

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703643

Seed Cotton Lint Cotton

Figure 1. Two-year average (1999-2000) seed and lint cottonyield following the application of poultry litter (PL) orcommercial fertilizer nitrogen in conservation andconventional tillage systems.

Eddie P. Millhollon, Associate Professor; JamesL. Rabb, Professor; Jose F. Liscano, ResearchAssociate; and Russell A. Anderson, ResearchAssociate, all at the Red River Research Station,Bossier City, La.

or two tons of poultry litter per acre, anda conservation plot that received fourtons of poultry litter per acre.

Poultry litter was applied in thespring with a spreader truck that wascalibrated to apply a rate of two tons peracre. For this study, the two-ton rateswere applied with a single pass and thefour-ton rate with two passes. The trucktraveled through the middle of each plot,and litter was spread with hydraulicallydriven disks mounted at the rear of thetruck. The litter was spread approxi-mately 35 feet (10 rows).

After litter application, all plotswere disked to incorporate wintervegetation and litter and bedded to form40-inch rows. Analysis of the poultry

M

Eddie P. Millhollon, James L. Rabb, Jose F. Liscano and Russell A. Anderson


Table 1. Soil chemical properties at 0 to 6 inches after three years ofapplying poultry litter or commercial fertilizer nitrogen in conservationand conventional tillage systems. (OM = organic matter)

P Na K Ca Mg OMTreatment ppm pH %

Conventional Tillage + 60 lbs. N/A 149 26 133 1037 309 7.60 1.05

Conventional Tillage + 2 Tons/A PL 195 25 154 770 245 7.40 1.05

Conservation Tillage + 60 lbs. N/A 136 24 113 843 264 7.58 0.89

Conservation Tillage + 2 Tons/A PL 203 29 164 1110 286 7.60 1.19

Conservation Tillage + 4 Tons/A PL 249 28 211 819 266 7.25 1.08

litter indicated that the three-yearaverage was 65 pounds per ton ofnitrogen, 33 pounds per ton of phospho-rus and 59 pounds per ton of potassium.

Cultural practices for cottonproduction recommended by the LSUAgCenter were followed. Plots that werefertilized received nitrogen (32 percentsolution at 60 pounds of nitrogen peracre) placed in the top of the row with aknife applicator. Rows in all plots wereshaped with a row conditioner toprovide a seedbed uniformly raisedto about 4 inches. Each year, a cottonvariety recommended by the LSUAgCenter was planted at the rate of10 pounds of seed per acre. The cottonvarieties planted contained the Bt andRoundup Ready genes that providedresistance to the cotton bollworm andtobacco budworm complex and toglyphosate herbicide. A pre-emergeherbicide, a seed-protecting fungicideand insecticide were applied at planting.

Poultry Litter Boosts YieldBecause cotton yield in 1998

was significantly reduced by a record

drought, yield data from that year werenot included in the summary presentedin Figure 1. Comparing the varioustreatments, two tons of poultry litter peracre with conservation tillage producedthe highest seed cotton and lint yield,followed by this rate of poultry litter ina conventional tillage system. Conven-tional tillage and 60 pounds of nitrogenper acre, considered a standard practicefor cotton production, resulted in the

lowest seed cotton and lint yield. Allplots that received poultry litter as a soilsupplement produced higher cottonyields than plots that received inorganicnitrogen fertilizer. Results indicate thattwo tons of poultry litter per acre appearto be the optimum rate because applica-tion of four tons of poultry litter actuallydecreased yield.

Litter Increases Soil FertilitySoil chemical properties at 0 to 6

inches resulting from the differenttreatments at the end of three-year studyare presented in Table 1. Increase in soilphosphorous and potassium content wasproportionate to the rate of poultry litterapplied and higher in these plots than inplots that received commercial fertilizer.This is understandable, given the levelsof phosphorous and potassium in poultrylitter and the fact that only nitrogen wasapplied to the other plots. Organicmatter at 0 to 6 inches was highest inconservation tillage plots that receivedtwo tons of poultry litter per acre,followed by conservation tillage plotsthat received four tons per acre. Sincetillage usually accelerates the break-down of organic matter, one wouldexpect organic matter to be lowest inplots that did not receive poultry litterand were conventionally tilled; it wassomewhat surprising to find that in plotsthat received 60 pounds of nitrogen peracre, conservation tillage plots werelower in organic matter than conven-tional tillage plots.

This study demonstrates thatpoultry litter can be effectively used as asource of nutrients for cotton productionin Louisiana with the added benefits ofimprovements in soil chemistry andorganic matter. It also demonstrates thebenefits of conservation tillage, particu-larly when poultry litter is used as a soilamendment.


A cotton field near Wisner, La.


otton defoliation, a critical stepin cotton production, is the process ofremoving leaves and preparing the cropfor mechanical harvest. Leaf removalfacilitates harvest and allows for moreefficient and faster picker operation,quicker drying of seedcotton, straighten-ing of lodged plants, retardation of bollrot and faster opening of green bolls. Inmany cases, chemicals that hasten theopening of green bolls and inhibitjuvenile regrowth are included with adefoliant.

Cotton defoliation research hasfocused on the efficacy of labeledcompounds. Environmental and cropconditions play a vital role. Most ofthese compounds are temperaturesensitive, and the closer the plant is tofull maturity, the more likely it is todefoliate well. Given the tremendousimpact of these variables on defoliation,results from research trials often varyamong locations and from year to yearwithin a given location. Therefore,cotton defoliation has sometimes beenreferred to as more art than science, and

only through a large amount of datacan clear trends emerge.

Proper timing of application fordefoliants is critical. Generally, themore mature and open the crop is, themore efficacious the defoliant. Prema-ture defoliation can result in highergrades, but it also can result in yieldloss. Delaying defoliation too long,however, can result in losses in yieldand quality caused by weathering andexpose growers to the risks of harvest-ing later in the season when tropicalstorms and wet conditions are morelikely.

Trials in Louisiana and other stateshave investigated two timing methods.One method is timing defoliation by thepercentage of open bolls of the crop.Most recommendations call for defolia-tion when 60 percent to 70 percent ofthe bolls are open. Another method iscalled nodes above cracked boll(NACB). Counting the number ofmainstem nodes between the uppermostfirst-position cracked and the lastharvestable boll on the plant determines

NACB. Most recommendations call fordefoliants to be applied at four NACB.

In 2000, trials were conducted at theNortheast Research Station in St. Josephand the Dean Lee Research Station inAlexandria. At St. Joseph, the highestyield was obtained at 42 percent openand 3.6 nodes above cracked boll; thehighest yield at Alexandria was foundat 75 percent open and 1.2 nodes abovecracked boll. The range in the findingsstrongly suggests that the boll distribu-tion on the plant must be consideredbefore applying any recommendedtiming rule. No recommendation islikely to fit every situation. Researchersare investigating the relationshipbetween the fruit distribution and thetiming of harvest aids.

In a three-year, replicated studyconducted in North Carolina, defoliationtiming was investigated in two varietiesof varying yield and quality characteris-tics. The study demonstrated the overallimportance of defoliation timing,especially in varieties that producerelatively high micronaire values.

In a similar North Carolina study,defoliation timing was examined incotton containing a mid- to late-seasonfruiting gap (late July to late August)resulting from insect pressure, fertilityproblems or any environmental stress.The results demonstrated that if nofruiting gap exists, cotton can bedefoliated as early as 50 percent openwithout realizing significant yield loss.If a fruiting gap exists, however,growers should delay defoliation untilapproximately 75 percent of the bollsare open to allow adequate time forplants to compensate for lost fruit. Instudies from other states, early seasonfruiting gaps (mid-July and earlier) havenot been found to alter defoliationtiming.

Both aforementioned studiesidentified a trend of increasingmicronaire and yield as the percentageof open bolls increased. Additionally,the node above cracked boll techniquewas examined in these studies for timingdefoliation and was found to be aseffective as the percent open technique.This is important for growers, because

Alexander M. “Sandy” Stewart, Assistant Professor and Extension Specialist, Dean Lee ResearchStation, Alexandria, La.; Donnie K. Miller, Associate Professor, Northeast Research Station, St. Joseph,La.; Joel C. Faircloth, Assistant Professor and Extension Specialist, Scott Research, Extension andEducation Center, Winnsboro, La.


Sandy Stewart, Assistant Professor at the Dean Lee Research Station, addresses a groupgathered for a field day at the Northeast Research Station, St. Joseph, La.

The Science of the ArtAlexander M. “Sandy” Stewart, Donnie K. Miller and Joel C. Faircloth

C

C O T T O N D E F O L I A T I O N


recording the nodes above cracked bollin a field takes considerably less timethan recording the percentage of openbolls.

Another area of defoliation researchfocuses on its economic return. It isoften less expensive for producers eithernot to defoliate, achieve less than 100percent defoliation or apply a desiccantto dry, but not actually defoliate, theleaves.

A large experiment was initiatedat the Dean Lee Research Station toinvestigate the effects of three levels ofdefoliation on cotton quality. The threelevels tested were clean 100 percentdefoliation, 20 percent desiccation ofgreen leaves and 20 percent greenjuvenile growth on the plant at the time

of harvest. The experiment was replicatedthree times, and harvested cotton wasstored in modules and ginned commer-cially to mimic commercial production asclosely as possible. Results indicate thatthe final loan value of the cotton washighest where 100 percent defoliationwas achieved. The source of discountsfor the less than 100 percent defoliationtreatments was primarily due to therelative yellowness of the bale samplesas classed by the U.S. Department ofAgriculture’s High Volume Instrumenta-tion (HVI) system. These data suggestthat there is an economic value todefoliation, but further research isongoing to determine the optimum levelof defoliation to make defoliant recom-

mendations as cost effective as possiblefor cotton producers.

In an effort to better understandcotton defoliation and make recommen-dations for producers, scientists in theLSU AgCenter continue to investigatethese and other areas of cotton defolia-tion. Future projects will focus onevaluating new products, defoliationtiming, application technology andeconomic returns to defoliation.

AcknowledgmentDonna Lee, Research Associate, NortheastResearch Station; and Derek Scroggs andBrad Guillory, Research Associates, DeanLee Research Station. The research waspartially supported by the CottonIncorporated State Support Committee.

Management systems that include reduced tillage and covercrops are gaining popularity. These practices typically increaseplant residues at the soil surface and organic matter in thesurface soil. In turn, microbial activity is increased, and the soildevelops a greater capacity to adsorb and retain many types offarm chemicals, including herbicides. Accordingly, tillage andcover crops variously affect the degradation of herbicides andtheir movement with surface water runoff and internal drainage.

TillageHerbicide degradation in soil is controlled by the interaction

of several factors. These include non-biological properties (suchas texture, organic matter and pH) and conditions (moisture andtemperature) and biological conditions (numbers, types andactivities of microorganisms). The main non-biological effect oftillage on herbicide degradation is probably increased herbicideadsorption onto soil solids because of increased soil organicmatter with reduced tillage. This has been shown for severaldifferent cotton herbicides including Bladex (active ingredient,cyanazine), Cotoran (fluometuron), Prowl (pendimethalin) andZorial (norflurazon), among others.

In some cases, increased adsorption of the herbicide inreduced tillage soils has led to its slower degradation and longerpersistence, despite typically higher microbial populations andactivities. But when the effect of adsorption on reducing theconcentration of herbicide susceptible to microbial degradationis factored out, it appears that degradation would actually befaster in the reduced tillage soils. These calculations suggest thatreduced tillage usually increases the rate of herbicide degrada-tion. But from the practical standpoint of how much herbicideactually remains over time, there is no clear, general conclusionon how tillage affects herbicide degradation rates.

Cover CropsAs with reduced tillage, planted cover crops increase soil

organic matter and microbial numbers and activities. Compari-son of herbicide adsorption in conventionally tilled soil with andwithout cover crops has shown that buildup of soil organicmatter because of the cover crop increases adsorption. But thedifferences in herbicide adsorption in reduced tillage soil be-cause of the cover crop tend to be smaller since levels of organicmatter are higher.

Given the ambiguous results for effect of tillage on herbicidedegradation, it is not surprising that there is no clear trend foreffect of cover crop. This is particularly true for reduced tillagesoil with cover crops. In some cases, increased herbicideadsorption caused by increased soil organic matter has led toslower degradation in soil planted with cover crops than soilwithout a cover crop. Whether this occurs may depend on thetype of cover crop and the biological and chemical properties ofits residue. For example, while there was no difference in thedegradation rate of Prowl in no-till Gigger silt loam soil withvolunteer native annuals or a wheat cover crop, degradation ofProwl was noticeably slower with a hairy vetch cover crop.

Besides effect of cover crop on herbicide degradation in soil,interception of spray-applied herbicide by crop and cover cropresidue in reduced tillage systems may affect herbicide degrada-tion and weed control. For example, Cotoran is relatively easilywashed off cover crop residue compared to Prowl. Conse-quently, interception of Cotoran by a dense layer of vetchresidue may have a negligible effect on herbicidal efficacy. On theother hand, since Prowl tends to be retained by residue, littleProwl that is intercepted by plant residue may ever be trans-ferred to the soil by rainfall. Instead, it is degraded by biologicaland chemical processes within the residue.

Lewis Gaston, Assistant Professor, Departmentof Agronomy, LSU AgCenter, Baton Rouge, La.


Tillage and Cover Crop Effects on Herbicide Degradation


rofitable cotton yields can be produced onLouisiana’s alluvial soils when limiting factorsare overcome. These include insect, nematodeand weed pests and water. Too much or too littlewater within the soil profile retards cotton rootdevelopment and nutrient uptake efficiency.Irrigation, properly applied, can increase yields,but improper management of irrigation can limityields. Although 40 percent of Louisiana cotton isirrigated, the optimal criteria for when to initiate,apply and terminate irrigation are lacking forLouisiana’s unsettled weather patterns.

The most important reason farmers irrigatecotton on Louisiana’s alluvial soils is to avoidcatastrophic yield losses from severe drought.This is crucial considering the costs of equipment,labor, seed technology, fertilizer and pest controlin the early part of the growing season. The mosteffective cotton irrigation schemes probably willtake several years to provide a return on invest-ment. Economic benefits from irrigation systemsmay be increased if producers rotate cotton with

other crops such as soybean, corn or rice, which have a higherwater-use demand. If producers choose to irrigate cotton onalluvial soils, timing is critical.

LSU AgCenter research focuses on low-input programsthat offer the best opportunity for producers to realize a returnon investment. Furrow irrigation tests were conducted on bothSharkey clay and Commerce silt loam on large commercialfields owned by the Panola Corp. and on Sharkey clay at theNortheast Research Station near St. Joseph, La. These tests

Irrigating Cotton

Steve Hague, former Assistant Professor and now with Bayer Cotton Seed inLeland, Miss., and Alphonse Coco, Research Associate, Northeast ResearchStation, St. Joseph, La.; and Donald J. Boquet, Professor, Macon RidgeResearch Station, Winnsboro, La.

Figure 1. Gross revenue return per acre of cotton lint andnumber of irrigation applications from schedules on Sharkeyclay in 2000 and 2001 at the Panola Corp., St., Joseph, La.

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Most of the cotton grown in Louisiana is grown in thesecolored areas. In addition, some cotton is grown justsoutheast of where the green and brown meet. The greenarea represents alluvial soils, which are optimal for cottongrowth. The yellow area represents the geologicalformation known as the Macon Ridge. The brown diagonalline follows the Red River. In the last five years, cottonacreage has ranged from 610,000 to 849,000, with anaverage farm gate value of more than $270 millionannually.

Overhead irrigation rigs are used but to a lesser extent than furrow irrigation.


Steve Hague, Alphonse Coco and Donald J. Boquet

on Alluvial Soils in Louisiana


compared the effectiveness of several schedul-ing techniques.

One of the systems included the ArkansasIrrigation Scheduler (AIS), a computerprogram developed at the University ofArkansas. The program recommends irrigationwhen soil moisture reaches a water-budgetdeficit designated by the user. Irrigationtreatments included a 2-inch (AIS 2.0) and 3-inch (AIS 3.0) deficit as well as a non-irrigatedcontrol. An AIS treatment (AIS 4.0) was testedin 2000, which allowed the soil moisturedeficit to reach 4 inches before irrigation andthen maintained a 2-inch deficit for the rest ofthe growing season.

A water-budgeting system developed atthe LSU AgCenter was included in the trials.This system assumes daily 0.22-inch wateruse and recommends irrigation when the waterbudget deficit reaches 1.5 inches (1.5 WB).U.S. Department of Agriculture cotton loanschedules were used to calculate gross revenuefrom lint per acre based on yield and fiberproperties from each treatment.

In 2000, less than 7 inches of rain fell in June, July andAugust, resulting in high irrigation demand. Responses toirrigation were observed (Figures 1 and 2) at Panola Corp.on both soil types. Performance of all irrigation schedulesexceeded non-irrigated control treatments. Schedules thatrequired the most frequent irrigation applications wereslightly advantageous in terms of yield and fiber quality;however, high gross returns were realized from regimeswith fewer applications.

In 2001 and 2002, timely rainfall occurred during thegrowing season. Damaging precipitation just before harvestcaused severe yield and quality losses in both years. At thePanola Corp. in 2001, AIS 2.0 performed well on both soiltypes and cotton responded better to 1.5 WB on Sharkey claythan on Commerce silt loam. The on-station tests showed littleto no economic benefit from irrigation in 2001 and 2002(Figure 3). In fact, plants suffered from mild waterloggingbecause of irrigation in 2002.

Figure 2. Gross revenue return per acre of cotton lint andnumber of irrigation applications from schedules onCommerce silt loam in 2000 and 2001 at the Panola Corp.,St. Joseph, La.

Figure 3. Gross revenue return per acre of cotton lint andnumber of irrigation applications from schedules on Sharkeyclay in 2001 and 2002 at LSU AgCenter’s Northeast ResearchStation, St. Joseph, La.

About 40 percent of the cotton grown in Louisiana is irrigated. Most irrigation is onthe ground using these plastic tubes.


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Research findings suggest small yield advantages and noeconomic benefit from irrigating cotton on alluvial soils inyears with normal to above-average rainfall. In a drought year,such as 2000, positive yield responses and economic benefitscan be expected from irrigation. Scheduling methods affectthe yearly number of irrigation applications and can influenceyield significantly. While AIS 2.0 most often maximized grossreturns, other schedules performed well and conserved morewater. AIS may be a viable option for scheduling irrigation,but other options are needed for Louisiana that will accountfor local conditions and needs of growers. Efforts are beingdirected toward developing an irrigation scheduling systemfor Louisiana cotton producers that is user friendly, optimizesyield and fiber quality, conserves water and maximizes profit.Studies are under way to determine the correct time to initiateand terminate irrigation using crop growth monitoring andalso to determine the interactions of irrigation with variousmanagement practices.


Table 1. Irrigated cotton lint yields, optimal N rates and costs andreturns in selected tillage and winter cover crop regimes, 8-yearaverage, 1995-2002.

Tillage and cover crop Lint yield Optimal Total Returnsnitrogen production above

rate costs* costs(lb/acre) (lb/acre) ($/acre) ($/acre)

No till, winter fallow vegetation 1116 80 418.32 162.00

No till, winter wheat cover crop 1113 90 435.45 143.31

No till, winter hairy vetch cover crop 1105 0 426.71 147.89

Surface till, winter fallow vegetation 997 70 417.21 100.78

Surface till, winter wheat cover crop 1058 120 470.66 79.85

Surface till, winter hairy vetch cover crop 1036 0 457.06 81.66

*Does not include land costs (rent) and general farm overhead costs.

arming practices can affectenvironmental and agronomicsustainability as well as productivity.Traditional farming practices in theMid-South typically use tillage andproduce one crop each year, whichexposes the soil to long periods withlittle or no protection from elementsthat cause sediment and nutrient losses.Multi-crop, year-round systems withsummer crops of corn, cotton, soybeanor grain sorghum combined withconservation tillage and winter cropsof wheat, rye or vetch green-manure areconsidered best management practices(BMPs). They can substantially reducefarm contributions to nonpoint-sourcepollution of surface water bodies. BMPsalso may benefit farm productivity,sustainability and profitability byimproving soil characteristics and cropperformance.

Two long-term field studies wereconducted at the LSU AgCenter’sMacon Ridge Research Station nearWinnsboro between 1987 and 2002 onGigger silt loam to determine the effectsof tillage practices, cover crops andnitrogen rates on cotton growth andyield. Cotton was grown continuouslywithout tillage (no-till) or with surfacetillage following annual winter covercrops of wheat, hairy vetch and volun-teer winter native vegetation and withfertilizer nitrogen rates of zero, 35, 70,105 and 140 pounds per acre.

Seedbed preparation of no-till plotsconsisted only of herbicide treatmentsfor vegetation control applied at leastthree weeks before planting. Seedbedpreparation in surface tillage treatmentsconsisted of four to five operationsincluding disking, bedding and bedsmoothing. No postplant cultivation was

used in either tillage regime. One of theexperiments was rain-fed, and one wasirrigated as needed. Other than experi-mental treatments, varieties, plantingmethods and management practiceswere those normally used in the area andrecommended by the LSU AgCenter. Alist of the treatments for both experi-ments and the identified optimal N ratesare shown in Tables 1 and 2.

An economic comparison of theabove cotton production systems wasperformed using enterprise budgets.Physical input-output data from theexperiments were used to develop anenterprise budget for each productionsystem. Actual input levels (fertilizer,

seed, herbicide) used were incorporatedinto the enterprise budgets. Equipmentsizes representative of commercialcotton farming operations were used toestimate costs on a per acre basis. Yieldswere estimated for each system at themean over the life of the experiment.Output prices used were essentiallycurrent loan rates under the 2002 FarmBill. Input prices were current inputprices used by the LSU AgCenter’sDepartment of Agricultural Economicsand Agribusiness to estimate 2002enterprise budgets for Louisiana.Constant prices and average yields wereused to compare the relative profitabilityof the various systems.

Table 2. Rain-fed cotton lint yields, optimal N rates and costs andreturns in selected tillage and winter cover crop regimes, 16-yearaverage, 1987-2002.

Tillage and cover crop Lint yield Optimal Total Returnsnitrogen production above

rate costs* costs(lb/acre) (lb/acre) ($/acre) ($/acre)

No till, winter fallow vegetation 728 45 339.61 38.99

No till, winter wheat cover crop 815 90 370.99 52.81

No till, winter hairy vetch cover crop 780 0 361.42 44.18

Surface till, winter fallow vegetation 749 45 347.80 41.68

Surface till, winter wheat cover crop 763 90 374.14 22.62

Surface till, winter hairy vetch cover crop 740 0 391.94 -7.46

*Does not include land costs (rent) and general farm overhead costs.

Donald J. Boquet, Professor, Macon RidgeResearch Station, Winnsboro, La.; Robert L.Hutchinson, Director, Northeast Region,Winnsboro, La.; and Kenneth W. Paxton,Professor, Department of Agricultural Economicsand Agribusiness, LSU AgCenter, Baton Rouge,La.

FDonald J. Boquet, Robert L. Hutchinson and Kenneth W. Paxton


Irrigated tillage, cover cropand N rate experiment,1995-2002

Cover crop biomass and N content.Following a cotton crop and withoutadditional fertilizer, the native, vetchand wheat cover crops produced anaverage 1054, 2054 and 4045 poundsabove-ground biomass per acre, respec-tively. Nitrogen concentration of thecover crop vegetation averaged 2.0percent in native, 4.0 percent in vetchand 1.5 percent in wheat. The totalamount of nitrogen in the cover cropbiomass averaged across year, tillageregime and nitrogen rate was 27, 90 and38 pounds per acre in native, vetch andwheat, respectively. As indicated by thelarge amount of nitrogen present in thevegetation, the vetch cover crop pro-vided sufficient nitrogen for productionof two-bale per acre cotton withoutapplication of inorganic fertilizernitrogen.

Cotton stand establishment.Seedling emergence and survivalaveraged about three plants per footof row and was little affected by tillagepractice or cover crop residue (data notshown). Although no-till cotton in the1970s and 1980s often experiencedreduced seedling emergence comparedwith tilled seedbeds, improvements inplanting equipment have alleviated thisproblem. The results of this study andthose of other researchers demonstratethat cover crop residue is not a majorhindrance to obtaining near-ideal plantdensity in no-till cotton fields. Withappropriate management and technologyuse, there is no longer an increase in therisk of production for no-till cottonfollowing a winter cover crop.

Cotton yields in no-till vs. tilledand cover crop versus no cover crop. Inthe initial years of the study, cotton lintyields in surface-till and no-till regimeswere similar but, after five years, no-tillyields were higher. No-till increasedcotton yield an average of 9 percent.The results demonstrate conclusivelythat, in the short and long term, cottonyields will not be reduced by no-tillpractices (Table1). The lowest yieldingtreatment was one in which no covercrop was planted and tillage was used.Further, the economic analyses of inputsand yield show that savings in equip-ment and labor costs contribute toincreased returns for cotton grownwith no-till practices (Table 1).

Interactions among cover crop,tillage and nitrogen rate. The optimal

nitrogen rate for cotton depended oncover crop and tillage regime (Table 1).Cotton following vetch needed nofertilizer nitrogen, and cotton followingwheat required high nitrogen rates foroptimal yield. When the optimalnitrogen rate was applied, however, alltillage-cover crop regimes producedsimilar yields. There was a larger yieldresponse in no-till than in surface-till foreach pound of applied nitrogen. Becauseunfertilized yields were lower in no-tillthan in surface-till, adequate nitrogenfertilization was needed for cotton tobenefit from no-till, especially followinga wheat cover crop. The fertilizernitrogen rate currently recommended forcotton following winter fallow-nativecover on loess soils may be too low forno-till cotton. There was no yieldresponse to fertilizer nitrogen followingvetch and thus no need to apply nitrogento cotton following vetch in eithertillage regime.

Rain-fed tillage, cover cropand N rate experiment,1987-2002

Lint yields in the rain-fed studywere lower than in the irrigated study,but the overall responses to cover cropand tillage were similar to the irrigatedstudy in that both no-till and cover cropincreased yield (Table 2). There wereimportant differences, however. Becauseof the lower yields in most years withrain-fed cotton, potential profitabilitywas much lower than with irrigatedcotton. With the lower yield potential,the opportunity for cotton to usefertilizer nitrogen was lower and thus

the optimal nitrogen rates were lower.The wheat cover crop was more benefi-cial to yield in rain-fed than in irrigatedcotton, probably because the residuehelped to conserve soil water. Highestyields and returns from rain-fed cottonwere produced using a combination ofa no-till seedbed and winter wheat covercrop.

No-till beats surface-tillNo-till cotton produced yields

similar to or higher than cotton plantedin surface-till treatments. Economicanalyses demonstrated that no-tillbenefits were augmented by lowerinvestments in equipment and laborcosts than surface till. Savings in tillagecosts in no-till were partially negated byincrease in chemical costs. The optimalnitrogen rate varied with tillage andcover crop from as low as zero poundsper acre to as much as 120 pounds peracre. The recommended fertilizernitrogen rate should, therefore, bespecific for each tillage and cover cropregime. Tillage, cover crop and nitrogenrate had significant but small effects onseedling emergence, yield componentsand plant growth variables, none ofwhich were deleterious to yield produc-tion. We conclude that the adoption ofno-till and winter cover crop BMPs toprotect the soil and water quality willnot decrease farm productivity orprofitability.

This is a field of no-till cotton growing in wheat residue.


AcknowledgmentThe studies in this report were partiallyfunded by Cotton Incorporated and theLouisiana Cotton Support Committee.


ransgenic technology, where genesconferring resistance to certain herbi-cides or protection against select insectspecies are transferred to plants, has hada dramatic effect on cotton production.According to National Cotton Councilfigures for 2002, more than 70 percentof Louisiana cotton acreage was plantedto transgenic varieties. Cotton varietiesresistant to herbicides glyphosate(Roundup Ready), bromoxynil (BXN)and glufosinate (Liberty Link) havebeen developed. Roundup Ready andBXN cotton have been commerciallyavailable for several years; Liberty Linkvarieties are to be available on a limitedcommercial basis in 2003. Use of thisnew technology creates the possibilityfor off-target movement, known as drift,onto nonherbicide-resistant cottonplanted in close proximity or for misap-plication from sprayer contamination.

To assess possible negative effects,research was conducted at the NortheastResearch Station in St. Joseph, La., in2000 and at the Macon Ridge ResearchStation in Winnsboro, La., in 1999 and2000. The methodology involved testingreduced rates of glyphosate (RoundupUltra formulation), bromoxynil (Buctril)and glufosinate (Liberty) on twodifferent cotton varieties (Stoneville474 at Macon Ridge and DP33B atNortheast) at three different growthstages (two-node, five-node and nine-node). Cotton response was assessedin seedcotton yield as well as in thefollowing: injury 14 days after treat-ment, plant height 30 days after treat-ment, dry weight 30 days aftertreatment, nodes above white flower,percentage open bolls and final plantpopulation.

Nontransgenic Cotton Responseto Off-target Herbicides

Roundup UltraBased on visual assessment, cotton

was more tolerant to glyphosate at thenine-node growth stage. Plant dryweight was reduced with glyphosaterates of 2 ounces per acre or higherapplied at the two- and five-node growthstages in two of three experiments.Weights were not affected by glyphosateat the nine-node stage. Plant height wasalso unaffected by lower rates, butreduction was noted for all growth stageby experiment combinations with theexception of nine-node for both experi-ments in 2000 with increase in herbiciderate of 2 ounces per acre or higher.Cotton maturity delay, as noted byincrease in node above white flower(NAWF) number, was observed onlyat the highest glyphosate rate appliedto two- and five-node cotton in one ofthree experiments. Percent open bolldata analysis indicated a decrease inchance of observing an open boll withincreasing glyphosate rate, and thiseffect was higher at the five-node stagecompared to the two- and nine-nodestages in two of three experiments.Although seedcotton yield was reduced9 percent to 13 percent for the highestrate when compared to lower rates, yieldfollowing glyphosate application wasequivalent to that for the nontreatedcontrol.

BuctrilBased on visual assessment, cotton

response was reduced as applicationtiming was delayed from two-to five-node in all experiments and from five-to nine-node in two of three experi-ments. Plant height reduction responsedecreased with increasing growth stageat time of application. Plant dry weightwas most negatively affected followingapplication at the two-node stage.Bromoxynil application, based on nodeabove white flower number (NAWF),did not result in maturity delays but didpromote earliness when applied at 4ounces per acre to two- and five-nodecotton in one of three experiments. Finalplant population was reduced only at the

two-and five-node timings, withresponse more pronounced at the initialtiming. Seedcotton yield followingbromoxynil application at the highestrate to two-leaf cotton was reduced 34percent compared with other rates andthe nontreated control, which wereequal. Bromoxynil applied to five- ornine-node cotton did not reduce yieldsignificantly.

LibertyBased on observation, cotton

response decreased as application timingwas delayed in one of three experiments.Injury response was slightly increasedwith application at the five comparedto two-node growth stage and was notsignificant for the latest applicationtiming (nine-node) in two of threeexperiments. In two of three experi-ments, plant height reduction responsewas lowest at the five-node stage andhighest at the nine-node timing. Regard-less of application timing, plant dryweight was affected negatively onlywith the highest rate of glufosinate.Glufosinate application, based on nodeabove white flower number and percentopen boll, did not result in a maturitydelay. Final plant population wasreduced in all experiments at the two-node application and in one of threeexperiments at the five-node timing.Glufosinate application did not affectfinal plant population adversely whenapplied to nine-node cotton. Negativeeffects on cotton growth were notmanifested in seedcotton yield reductionfollowing glufosinate application.

Prevention Is BestAlthough various negative effects

on growth were observed followingapplication of Roundup Ultra, Buctrilor Liberty herbicides at rates simulatingthose experienced with drift and sprayercontamination, cotton was able torecover and yields were equal tonontreated plants in almost every case.Yield reduction was observed only withBuctril at the highest rate (4 ounces peracre) applied to cotton in the least

Donnie K. Miller, Associate Professor, NortheastResearch Station, St. Joseph, La.; Robert G.Downer, Associate Professor, Department ofExperimental Statistics, LSU AgCenter, BatonRouge, La.; Steve T. Kelly, Assistant Specialist(Weed Science), Scott Research, Extension andEducation Center, Winnsboro, La.; and P. RoyVidrine, Professor, Dean Lee Research Station,Alexandria, La.

T

Donnie K. Miller, Robert G. Downer, Steve T. Kelly and P. Roy Vidrine


advanced growth stage (2-node).Although the cotton was able to recoverfully, it should be noted that late-seasongrowing conditions were optimum at alllocations because of supplementalirrigation at Winnsboro and adequaterainfall at St. Joseph. Cotton wasmanaged for insect pests throughout theseason. Had environmental conditionsbeen less than optimal, the growingseason shortened or insect damagemore extensive, cotton may not havebeen able to recover fully, and detrimen-tal effects from herbicide applicationmay have caused yield reduction. In

Donnie K. Miller, Associate Professor, Northeast Research Station, St.Joseph, La.; P. Roy Vidrine, Professor, Dean Lee Research Station,Alexandria, La.; Steve T. Kelly, Assistant Specialist (Weed Science),Scott Research, Extension and Education Center, Winnsboro, La.; andRebecca G. Frederick, Research Associate, Department ofExperimental Statistics, Baton Rouge, La.

Conservation tillage systems, whether no-till or staleseedbed, require use of herbicides before crop planting to ridfields of native winter vegetation and planted cover crops.Elimination of competing vegetation, which is called burndown,helps improve soil moisture and assure crop stand establish-ment, rapid early season growth and efficient fertilizer use.The herbicide 2,4-D is used in burndown weed controlbecause it eliminates a number of problem broadleaf winterweeds at a relatively low cost.

One problem with 2,4-D is that even though applied post-emergence, it can stay in the soil long enough to injuresensitive crops such as cotton. The injury is more likely tooccur if cotton is planted shortly after herbicide application.Unfortunately, most 2,4-D herbicide labels indicate no strictplant-back interval and include vague language such as “90 daysor until dissipated from the soil.” The LSU AgCenter isparticipating in a regional research collaboration to assessplant-back intervals to cotton following application of 2,4-D.

As part of this research, studies were conducted in 2001and 2002 at the Northeast Research Station in St. Joseph, theDean Lee Research Station in Alexandria and the Macon RidgeResearch Station in Winnsboro to assess effects of 2,4-Dapplied at various preplant intervals on growth and yield ofcotton. The 2,4-D was applied in two formulations, amine andester. The two 2,4-D formulations were applied at the labeledrate and twice the labeled rate to rows undisturbed beforeapplication.

In 2001, each herbicide was applied seven, 14 and 21 daysbefore planting. In 2002, application intervals were seven, 14and 28 days before planting. A nontreated control wasincluded for comparison. Cotton was planted and maintainedweed free by hand-hoeing or postemergence herbicide. Todetermine possible negative effects, these assessments weremade: visual injury, plant height, plant population about 30days after planting and seedcotton yield.

Visual injury as high as 70 percent at St. Joseph in 2001 and22 percent at Alexandria in 2002 was observed on cottonfollowing a 2,4-D application before planting. For both loca-tions, differences in injury could not be detected between

herbicide formulations or rates, or among application inter-vals. Injury was either not observed or negligible at St. Josephin 2002, Alexandria in 2001 and Winnsboro in 2001. Differinginjury response among experiments could not be explained byrainfall patterns before or after 2,4-D application.

Although significant injury was observed in two of fiveexperiments, plant height and population and seed-cottonyield were not reduced at any location when compared tocotton receiving no preplant application of 2,4-D. At St. Josephin 2001, extreme variability in the data may have reduced theability to detect differences on cotton growth and yield.Results indicate that 2,4-D can be applied seven days beforecotton planting without having negative effects on growth andyield. Cotton was able to recover from this early season injuryand compensate because of a full growing season and intensivescouting and management of weeds and insects. Under differ-ent growing conditions, cotton may not have been able torecover fully.

Although results of this study support 2,4-D label changes,such changes must be initiated by the herbicide manufacturerand approved by the U.S. Environmental Protection Agency.Producers are cautioned to follow current label restrictionsfor planting cotton following 2,4-D application.

AcknowledgmentDonna R. Lee and A. Lawrence Perritt, Research Associates,Northeast Research Station; Derek Scroggs, Research Associate,Dean Lee Research Station; and Barrett McKnight, ExtensionAssociate, Scott Research, Extension and Education Center, fortheir work and Helena Chemical Company for providing funding.

AcknowledgmentDonna R. Lee, A. Lawrence Perritt,C.F. Wilson and J.L. Milligan, ResearchAssociates, Northeast Research Station,St. Joseph, La., for their work and CottonIncorporated for providing funding.

Effects of Pre-plant Application of 2,4-D on Cotton

addition, rates observed in these studiesare representative of those that would beexpected in drift or sprayer contamina-tion situations, and higher rates mayresult in more deleterious effects.Therefore, producers are cautioned totake all measures to avoid herbicide driftand sprayer contamination.


Non-profit Org.U.S. Postage

PAIDPermit No. 733Baton Rouge, LA

Louisiana Agricultural Experiment StationLouisiana State University Agricultural CenterP.O. Box 25100Baton Rouge, LA 70894-5100

Inside:

For more than 100 years, cottonhas been the most important cropgrown in Northeast Louisiana. Read aperspective on cotton’s role in thestate’s economy. Page 4

LSU AgCenter research has playeda significant role in making it possibleto grow cotton profitably in this state.

Page 6

Scientists are learning more aboutprecision agriculture by studyingremote sensing images. Page 9

Conservation tillage in cottonimproves water quality.

Page 32

Photo by Mark ClaesgensGene Burris (standing in striped shirt), a professor at the LSU AgCenter’s Northeast Research Station at St. Joseph,La., explains to farmers gathered for a field day about the research he is conducting to determine how to usetechnology to better control nematodes. The research involves using a Veris mapping cart, the wheeled device atright, to measure soil conductivity. See more explanation of the research on page 11. Others in the photo are, left toright, Richard Costello, post-doctoral researcher, and Libby Byrnes and Mirandy Lee, both student summer workers.Maurice Walcott, research associate, is standing under the umbrella.

Documents

Cotton Issue - LSU AgCenter/media/system/7/5/9/7/... · Louisiana’s cotton farms have changed dramatically in the past 50 years. In the early 1950s, the average cotton farmer grew