Codling Moth Management with New Insecticidesentomology.tfrec.wsu.edu/jfbhome/growerarticles/cm management with... · insecticides requires an understanding of ... (mainly in pear),

M. Doerr and J. Brunner – WSU TFREC Not for publication

Presented at:Codling Moth Symposium 2003

1

Codling Moth Management with NewInsecticides

Mike Doerr and Jay BrunnerWashington State University

Tree Fruit Research and Extension CenterWenatchee, WA

Codling moth (CM) is the "key" pest ofpome fruit in Washington. Recently,CM densities have begun to increase inmost growing areas of the state. A CMcontrol program that is reliant on onetactic is inherently less stable than oneusing multiple tactics. This is especiallytrue as increasing pest pressure threatensa grower’s ability to produce amarketable crop. If a grower is using aninsecticide-based program it is wise toconsider using products with differingmodes-of-action. If using matingdisruption then supplementalinsecticides should be applied whenneeded.

A continued reliance upon theorganophosphate (OP) class ofinsecticides (e.g. Guthion or Imidan) asthe primary chemical control tactic isbecoming more difficult under thecurrent regulatory environment. Pastresearch has documented that CM havedeveloped resistance to OPs, whichthreatens the excellent level of controlgrowers have come to expect. It islikely, though not proven yet, that recentcontrol problems with CM stem fromincreased levels of OP resistance. Theregistration of new insecticides withdifferent modes-of-action and with highselectivity provide management optionsthat can be used in conjunction witheither an insecticide- or matingdisruption-based CM management

program. The knowledge level requiredto manage CM increases as growersmove away from a strategy reliant onlyon OP sprays. A careful and thoughtfulapproach to incorporating newinsecticides into the managementprogram will ensure the best possiblecontrol of CM, improve control of someother pests, e.g. leafrollers, and conservemore natural enemies.

Bringing new insecticides to market:Although the Food Quality ProtectionAct of 1996 (FQPA) has resulted inrestrictions on the use of OP insecticidesin pome fruit production, it has allowedfor expedited registration of newinsecticides under the “reduced risk” and“OP alternative” programs. Anunanticipated consequence of this actionis that new insecticides often receiveregistration before researchers have hadthe opportunity to fully understand theirrole in the orchard environment. It isour hope that growers appreciate themeasured steps researchers take beforerecommending a new insecticide for aspecific pest.

Four methods are used to evaluate thepotential of new insecticides:

• Laboratory bioassays• Field-Aged bioassays• Small-plot field trials• Large-plot field trials



2

Laboratory bioassays: Using a variety oftechniques (e.g. direct sprays, apple-dipor leaf-dip bioassays) the toxicity ofcandidate insecticides is evaluated in thelaboratory. These bioassays provide ameans of determining relative toxicityand whether further testing is warranted.Insecticide manufacturers have a generalidea as to which group of insects areaffected by their experimental product,but local researchers have the ability totest new insecticides against the pestscommon to a specific region. Laboratorybioassays can also be used to screen newinsecticides against a variety ofbeneficial insects. Further, thesebioassays form the basis of resistancemonitoring. A concentration of aninsecticide that kills 50% of the pest iscalled the LC50. These LC50 values aredetermined for new insecticides using asusceptible laboratory maintainedpopulation and provide “base-line” dataon the pest’s susceptibility. Thisinformation can then be compared toLC50 values obtained from field-collected populations of the pest to see ifresistance to the new insecticide ispresent or has changed over time. Anysignificant shift in toxicity noted in field-collected populations suggests thattolerance or resistance could limit theefficacy of a new insecticide incommercial orchards.

Field-aged bioassays: This techniqueinvolves spraying a candidate insecticideonto individual trees and then collectingand returning foliage or fruit to thelaboratory at regular intervals to assessresidual toxicity. Field-aged bioassaysare used to identify the best rates andtreatment intervals to use.

Small-plot field trials: Once a good ideaof an insecticides rate range isdetermined from field-aged residuebioassays field-trails are initiated. Inthese trials the insecticide is applied toreplicated, single-tree plots using ahandgun sprayer. A relatively large anduniformly distributed pest population isneeded for this type of trial. To maintainstandardization among all treatmentsthey are applied at full dilute rates toensure excellent coverage of foliage andfruit. Thus, confounding factors ofcoverage or concentration are eliminatedand the results tend to be consistent andrepeatable. An effort is made to evaluatecandidate insecticides in a number ofdifferent locations under a variety of pestpressures. This allows researchers toadjust rates and modify timing intervalsgaining an understanding of how theinsecticides perform in differentsituations. Small-plot field trialstargeted for one pest allows a glimpse atthe selectivity of the insecticide. It cantake three years or more of testing beforeresearchers are confident ofrecommending a use pattern that best fitsthe conditions and pest complexes of theregion.

Large-plot field trials: Large-plot fieldtrials are an important step inunderstanding how a new insecticidewill fit into a pest management program.The small-plot trials can determine rateand interval information for a particularpest but are not robust in identifyingother positive or negative effects on theorchard ecology. In these tests aninsecticide is applied by an air-blastsprayer at rates and volumes usedcommercially. The effect of a newtreatment program is then evaluated bycarefully sampling all pest and beneficialarthropods. These trials are labor



3

intensive and costly but reveal the fullimpact of a new insecticide implementedas a grower would. These kinds of trialsneed to be evaluated at the same locationfor more than one year to gain a trueunderstanding of any long-term changesin orchard ecology.

A consequence of rule changes underFQPA is that pesticide companies nolonger obtain Experimental Use Permits(EUP) to allow for large plot fieldtesting prior to final registration. That isbecause they would have to give up aposition in the EPA registration cue,replacing another insecticide they wantregistered, and the data required for anEUP is essentially the same as for fullregistration. The result has been to limitthe ability of researcher to evaluate newinsecticides using typical growerpractices. Due to this limitation, theimpact of a new insecticide is typicallynot fully understood at the time ofregistration. Therefore, large-plot fieldtrials are generally conducted after aninsecticide is registered delaying theoptimized recommendations on how touse them coming from unbiased sources.

Alternative insecticides for CM: Wewould like to explore use patterns for aselect number of insecticides that havethe potential to be substitutes orsupplements in insecticide-based ormating disruption control programs. Bydefinition, the use of these productsshould be considered alternative orsupplemental control measures within apest management strategy targetingcodling moth. A grower needs to utilizethe specific modes-of-action of theseproducts to help protect against high-risksituations. It is expected that a growerwill select portions and/or combinationsof the programs detailed below to

establish a successful, site-specific, CMmanagement program.

An educated approach to utilizing theseinsecticides requires an understanding ofthe targeted life-stage that is based onspecific modes-of-action of theseproducts. The insecticides that will becovered in this paper are:

• Horticultural oil• Granulosis virus• Entrust/Success• Intrepid• Assail

Horticultural oil: WSU-TFREC hasconducted an extensive evaluation of thesummer use of oil and has establishedthat repeated applications of highlyrefined horticultural oils can be madesafely under most circumstances. It isthought that the repeated use of oilduring the summer has the potential toaffect fruit quality and even tree vigor,but solid data demonstrating this underour conditions has yet to be fullydocumented. A grower must balance theuse of oil for codling moth control withpossibility of enhanced fruit maturity(mainly in pear), a greasy coating thatmay inhibit wax deposition, an increasein sunburn, and possible long-termhorticultural effects.

The oil we have the most experiencewith is Orchex 796. This product formsthe base for many oil products that arereformulated by agricultural chemicaldistributors. The life-stage targeted byoil is the egg and the mode-of-action isas an oxygen barrier, which suffocatesthe egg (Table 1). Oil is primarilyeffective when it is applied on top ofeggs, thus any egg laying activity ofadult moths after an oil application



4

should be considered unaffected. Issuesaffecting the level of CM control are:

• Water volume/coverage• Concentration of oil (v:v)• Frequency of application• Rate (gallons) of oil/acre

It is essential that the volume of waterused assure complete coverage of thefoliage and fruiting surfaces. However,too much water can result in oil runningand pooling on foliage and fruit where itis concentrated during drying. It isunder these conditions that fruit markingof foliage burn is most often observed.Laboratory and field trials havedemonstrated a concentration-basedeffect with oil. While there is someeffect of concentrations above 0.25%,the most consistent results have beennoted with at least a 1% v:vconcentration. Increasing rates above1% can increase efficacy slightly but therisk of phytotoxicity on foliage or fruitalso increases. Under high pressure, anincreased frequency of applications isnecessary to ensure that eggs depositedafter one application do not hatch priorto the next spray. Water volume,concentration and frequency ofapplication all affect the amount ofoil/acre that is applied to trees. It islikely that the amount of oil/acre has themost influence on undesirablehorticultural responses.

Granulosis virus: CM Granulosis virusoccurs naturally. It is relatively easy toperpetuate in a colony but becomesconsiderably more difficult to formulateinto an insecticide. Many virus productshave been introduced into themarketplace, but the virulence (potency)of these products has varied. Qualitycontrol of the virus and its formulation

by the manufacturer is critical. The bestresults can be expected from a productthat has a proven history. Calliope ofFrance produces Carpovirusine. Wehave experience with Carpovirusine thatdates back to 1995, and this product hasbeen used extensively in Europe sincethat time. This product is now availablefor use in North America. Other virusformulations that are also beingintroduced into the market place mayhave good qualities but unless we havetested them we cannot and will notrecommend their use.

The target of CM granulosis virus is theneonate (newly hatched) larva. ActiveCM granulosis virus is very specific,affecting only CM, and it is highlylethal. Virus particles must be ingestedprior to the larva entering the fruit to beeffective and have the maximum cropprotection value (Table 1). Granulosisviral DNA is released in the alkalineenvironment of the insect gut. The viralDNA attacks cells of the insect, therebydisrupting normal physiology. InfectedCM larvae turn milky white prior todying. Dead larvae appear to “melt”,releasing an oozing substance that is fullof virus particles. While mortality canoccur rapidly in neonate larvae if enoughvirus particles are ingested it is oftendelayed and under high-pressuresituations there is little reduction in fruitinjury. The virus continues to work onCM larvae even after they enter the fruitor even if they complete developmentand move to a pupation site. The fulleffect of the virus is not noted untilsubsequent generations when thepopulation does not increase asexpected.

There are issues remaining to beinvestigated regarding the long-term



5

effect of granulosis virus on the CMpopulations where delayed mortality andsublethal effects may be common. Inaddition, the natural persistence of theviral DNA in the CM population needsto be explored. Research on the use ofCarpovirusine in Washington is limitedand thus fine-tuning of rates andtreatment intervals is still necessary.However, this product does offer theorganic grower another tool incombating their more serious insectthreat.

Entrust/Success: Growers have beenusing Success (spinosad) to successfullymanage leafroller and Lacanobiafruitworm for several years. The use ofSuccess against CM in conventionalorchards has not been recommended,though we have known it has activity, inorder to preserve its use for these otherpests. An organic formulation with thesame active ingredient as in Success,spinosad, has recently been registeredand is marketed under the name Entrust.This opens the door to the possible useof spinosad against CM in organicorchards where there are few otheralternatives.

The target of Entrust is the neonatelarva. Entrust must be ingested to beeffective, that is, prior to or as the larvaenters a fruit (Table 1). Entrust is anervous system toxicant acting at thesynapse. All research on the efficacy ofspinosad against CM has been done withthe Success formulation. We willassume for sake of this discussion thatthe Entrust formulation will worksimilarly. Our research with Successshows that the residual activity is thelimiting factor in CM control.Therefore, more frequent applications atlowered rates should enhance efficacy.

We feel that control with Entrust will beimproved if combined with an oilprogram that would utilize two modes ofaction attacking two life stages.

Intrepid: Intrepid (methoxyfenozide) isan insect growth regulator (IGR) thatmimics a hormone specific tolepidopteran insects. This IGR is aninsecticide that is very active against twolife stages; against eggs as an ovicideand larvae as a larvicide (Table 1). Acommon term to describe this class ofIGR is Molt Accelerating Compound.As this name suggests, ingestion of thechemical by larvae stimulates a molt.Since this hormone mimic is not perfect,the larva is not able to complete the moltand dies. The mode of action against theegg stage is not as well understood but itdoes stop the egg from developingcompletely.

The length of residual control of Intrepidappears to be longer than Success, thustreatment intervals of 14 days should beeffective. Delayed mortality is notuncommon and neonate CM larvae mayenter under the fruit skin before dying.If this occurs during the first generationthe injury will likely scar-over and notresult in a downgrading of the fruit atharvest. However, if populations arehigh in the second generation these“stings” may result in significant fruitinjury. While “stings” might not beacceptable if populations of CM are toohigh they are not a true reflection ofIntrepid’s effect on the population. Theshallow stings produced by larvae thateventually die will does not mean thatthe orchard will have a serious carryover problem the following year.

Assail: Assail (acetamiprid) belongs to anew class of chemistry called



6

chloronicotinyl. Assail has performedconsistently and with a high degree ofefficacy in several trials, and is the mostactive of the new insecticides nowregistered for CM control. The target ofAssail is the neonate larva. Assail mustbe ingested prior to the larva entering afruit (Table 1). Assail is a neuro-activeinsecticide that works at the synapse toparalyze an intoxicated insect.

The chloronicotinyls have beenimplicated in disruption of integratedmite control. The exact cause of miteflare-ups with this class of chemistry isnot well understood, but as a precautionthe manufacturer recommends theaddition of 1% oil to an Assail spray toassist with spider mite suppression.

A review of the products available tomanage CM (Table 1) shows that thereare viable options to attack all lifestages. It will be the proper combinationof these insecticides with the old reliabletools of Guthion (azinphos-methyl) orImidan (phosmet) and mating disruptionthat will be the key to a successfulmanagement of CM in 2003, even whenfaced with situations of high pressure.

Codling moth phenology: Theinsecticide alternatives to OPs describedabove have very specific modes ofaction, and vary in their residual activity.Thus a thorough understanding of theCM life cycle is necessary to accuratelytime their applications to assure controlof the targeted life stage and eliminatewaste.

The life cycle graphs presented below(Fig. 1) are developed from predictionsgenerated by the widely used CMdegree-day (DD) model. Modelpredictions are based on normal CM

development and in no way replace asound monitoring program.

Table 1. Summary of viable supplementalcodling moth insecticides.

InsecticideTargetlife stage Mode of action

Orchex 796 Egg AsphyxiationCarpovirusine Larva Disrupt cell

physiologyEntrust Larva Disrupt nerve

transmission at thesynapse

Intrepid Egg

Larva

Disrupt normalcell division

Molt AcceleratingCompound

Assail Larva Disrupt nervetransmission at thesynapse

WSU-Tree Fruit Research and Extension Center

0 100 300 500 700 900 1100 1300 1500 1700 1900 2100 2300

DD from biofix

Predicted flight

Bloom

Mid August

???Jun 25- Jul 10

Full season CM phenology


Full season CM phenology

0 100 300 500 700 900 1100 1300 1500 1700 1900 2100 2300

DD from biofix

Predicted flight

Predicted hatch

???

Predicted ovipositionBloom

Mid August

Jun 25- Jul 10

Figure 1: Codling moth model predictions for theadult flight (A), oviposition (B) and hatch (B).

The CM “season” begins with adultflight, which traditionally has occurredat the same time as full bloom in



7

Delicious apples. The flight lasts about800 DD (Fig. 1A). The second flightbegins at approximately 850 DD andends near 2000 DD. CM responds toshortening day length, a signal to maturelarvae to enter diapause. In our area thistrigger occurs about August 15 eachyear. Only those larvae that pupate priorto mid-August will continue theirdevelopment and emerge as a partial 3rd

generation. The size of this 3rd

generation is dependent on how quicklythe first and second generations develop,or in other words how many DD areaccumulated prior to mid-August. Aswe get closer to mid-August it ispossible to estimate the amount of 3rd

generation activity that might occurwithin a region. If a large 3rd generationis predicted and control of theproceeding generations was not good,growers will need to respondappropriately to protect their fruit.

CM females emerge slightly after themales (50 DD) and begin laying eggsaround 70-80 DD. Eggs requireapproximately 150 DD to hatch. Thepredicted oviposition and hatch curvesare offset from the male flight curveaccordingly (Fig 1B). These predictedcurves will be used to demonstrateappropriate use patterns for differentinsecticides in CM control.

Optimizing insecticide treatmentsHorticultural oil: To review, oil isapplied over the CM eggs to smother thedeveloping embryo. In order to optimizeuse, oil sprays need to begin prior to egghatch (230-250 DD) and repeated atregular intervals to cover the entireoviposition period. In a typical scenariothe first spray is applied at 200 DD, andrepeated at 400 and 600 DD (Fig. 2).These timings generally cover the

majority (90%) of the first ovipositionperiod. Abnormal moth activity, such aslate flights in a generation, is notuncommon and would leave fruitunprotected using this protocol.


Oil to kill eggs

0 50 100 200 300 400 500 600 700 800 900 1000 1100 1200DD from biofix

Predicted oviposition

standard timing

Unprotected


Oil under heavy pressure

0 50 100 200 300 400 500 600 700 800 900 1000 1100 1200DD from biofix


Weekly intervals

Unprotected

Figure 2: Timing of oil to control codling motheggs during the 1st generation using the standardtiming (A) or weekly under high pressure (B).

In orchards under high-pressure thefrequency of applications must increaseto maintain control of CM eggs andassure significant hatch doesn’t occur inthe interval between applications. Themost aggressive program utilizes asmany as 6 sprays during the 1st

generation alone (Fig. 2B). Plottingthese weekly applications on a DD scaleshows that oil may be applied relativelymore frequently earlier in the generationdue to fewer DDs accumulated duringthe cooler days. This can be consideredbeneficial, though, as the majority ofoviposition generally occurs during the



8

early part of the generation. The moreintensive oil program leaves a smallerportion of the period betweengenerations unprotected.

Entrust: Entrust (Success) is a larvicidethat must be ingested by young larvaeprior to entering the fruit to be effective(Fig. 3). This product has not ovicidalactivity. Entrust applications must betimed to coincide with egg hatch as thelength of residual control is relativelyshort (10 to 14 days). The level ofcontrol expected from Entrust is modestand combining it with an oil programshould maximize control and thereforefruit protection. The combination withan oil program enlists two differentmodes of action targeting two life-stages. The spray program detailed inFig. 3 shows oil applied at one-weekintervals (black arrows) with Entrustadded combined with the oil every otherweek (red arrows) to cover the entirehatch period.

Codling moth granulosis virus: Thesame strategy used for controlling CMwith Entrust could be used for thegranulosis virus (Fig. 3). Young CMlarvae must ingest virus prior to enteringfruit to be effective. Granulosis virus isextremely toxic to CM, but larvaegenerally ingest only a small amount andit may take several days for viral DNAto replicate to the point that deathoccurs. Therefore, it is important torealize that injury in the form of “stings”will likely occur but that is notnecessarily an accurate measure of theefficacy of granulosis virus. Often thefull effect is not noted until thefollowing generation. To maximize fruitprotection granulosis virus should becombined with an oil program. Entrustand granulosis virus are best suited for

organic orchards where other viablecontrol alternatives are limited.


Adding Entrust or virus to oil program

0 50 100 200 300 400 500 600 700 800 900 1000 1100 1200DD from biofix

Predicted hatchLower rate- more spraysPredicted oviposition

Figure 3: Adding Entrust or Granulosis virus toan oil program during the first generation. Redarrows designate a combination oil/Entrust(virus) spray.


Intrepid used as ovicide

0 50 100 200 300 400 500 600 700 800 900 1000 1100 1200DD from biofix

100 DD timinggood for LRs

14 d 14 days 14 days

Predicted hatch



Intrepid used as larvicide

0 50 100 200 300 400 500 600 700 800 900 1000 1100 1200DD from biofix

-250 DD timing extends residual-Better timing for Lacanobia

14 days 14 days 14 days

Predicted hatch


Figure 4: Two Intrepid programs starting at anovicide timing, 100 DD (A) or larvicide timing,250 DD (B).

Intrepid: Intrepid has a unique mode ofaction that makes it active against botheggs and larvae. Laboratory bioassays



9

and field-trial data suggest that there islittle difference between starting Intrepidsprays at the traditional ovicidal (50-100DD) or larvicidal (250 DD) timings (Fig.4).

The decision of how to incorporateIntrepid into a pest managementprogram should be based on expectedpressure from secondary pests. The 50-100 DD timing is right around the petalfall period, which is the optimal timingfor spring leafroller control. Delayingthe first application to 250 DD may bethe best option if noctuid pests such asLacanobia subjuncta or BerthaArmyworm are the main concern. Inorder to maximize fruit protectionIntrepid should be sprayed at 14-dayintervals.


Assail + 1% oil for mites

0 50 100 200 300 400 500 600 700 800 900 1000 1100 1200DD from biofix

Predicted hatch

21 days 21 days

Figure 5: Timing Assail to control codling mothlarvae of the 1st generation.

Assail: Assail is a larvicide that must beingested prior to larvae entering the fruitto be effective. Of all the newchemistries Assail behaves most like thetraditional CM insecticides (e.g. Guthionand Imidan). Assail is a fast actinginsecticide with a relatively long residualperiod. An Assail use pattern will bevery similar to a Guthion program (Fig.5). The manufacturer of Assailrecommends that its use be combined

with 1% oil. The oil is added tosuppress the resident mite population.Assail, as well as other chloronicotinylinsecticides has been implicated incausing increased spider mite densities.Therefore, the use of Assail should belimited to a role as one of differentproducts used to control CM rather thana strict Guthion replacement.

Creative combinations employingdifferent modes of action: IPMpractitioners can use their creativity tooptimize spray timings. Creating newspray programs requires a soundunderstanding of the CM lifecycle,insecticide mode of action, and a reliablemonitoring program. The exampledetailed in Fig. 6 illustrates the use of atank mix of Intrepid/Assail applied at250 DD to control CM during the firstgeneration. Assail residues will controlhatching CM larvae for about 21 days(300-400 DD) after application. Whichwill cover most, ca. 70% of the predictedegg hatch period. Intrepid will suppresshatch of eggs deposited prior toapplication if coverage is sufficient.Further, it will kill CM eggs depositedon top of residues for 14 days (200-250DD). These are eggs that would havestarted hatching at 450 DD or after mostof the Assail residue had worn off. Inaddition the larvicidal activity ofIntrepid residues will help with thecontrol of larvae. This strategy managesthe CM population with a single sprayby combining the different modes ofaction. However, the orchard issusceptible to late activity so special careshould be made to monitor during thattime period.

Second Generation: Spray programstargeting the second CM generationmust take into account a longer



10

emergence pattern (Fig. 7). It is probablymore important to monitor orchards inthe second generation to see if theactivity in the orchard is agreeing withthe model predictions. Modelpredications are not as reliable for thesecond generation. Spray timings basedon the CM degree-day model may befurther confounded by the presence of apartial third generation. The size of thisgeneration is variable and based on howquickly the first two generationsdevelop.

Ovicidal sprays: The standard oil timingof 1200, 1400 and 1600 DD cover lessthan 70% of the oviposition period (Fig.7A). This leaves a large portion of the2nd generation, as well as any 3rd

generation activity, uncontrolled.

Larvicidal sprays: The extended hatchperiod of the second generationchallenges the residual limits of a twocover spray program (Fig. 7B).Assuming 21 days of residual control,this program covers most of the 2nd

generation and the beginning of the 3rd

generation. If 21 days of residualcontrol cannot be expected, furthercontrol decisions must take into accountrelative CM pressure, as well aspreharvest and re-entry intervals.

What level of control can be expected?Codling moth has the capacity toincrease population levels quickly in theabsence of chemical control, even if weassume a very high level (80%) ofnatural mortality (Table 2). A CMmanagement program needs to suppressthe population by an additional 90% justto maintain the same number of CM. Ifa management program is not able toprovide this level of suppression thepopulation will grow exponentially. It is

common for us to see the damage levelof CM in our untreated plots increasefrom 0.5% at harvest the previous year,to between 5-10% after the firstgeneration the next year and at harvestof that year fruit damage could easily bebetween 30-50%.


Combining modes of action targeting two life stages with one spray

0 50 100 200 300 400 500 600 700 800 900 1000 1100 1200DD from biofix

Assail larvicide

Predicted flight

Predicted hatch


Intrepid ovicide

Vulnerable to late activity

Figure 6: Employing different modes of actioninto one well-timed spray.


2nd generation Oil program

900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300

DD from biofix


???

Standard timing

Unprotected


2nd gen. standard control- 21 d residual

900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300

DD from biofix

Predicted hatch

???

17 Jul-8 Aug 8 Aug- 29 Aug

Figure 7: Spray programs targeting oviposition(A) and hatching larvae (B) during the 2nd CMgeneration.



11

Table 2: Exponential CM growth under a varietyof insecticide control programs.

Total number of CM adults*(Control from IPM program)Year/

Generatn 0% 50% 75% 90%2000-1st 1 1 1 12000-2nd 10 5 3 1

2001-1st 100 25 6 12001-2nd 1,000 125 16 1

2002-1st 10,000 625 40 12002-2nd 100,00

03,125 100 1

2003-1st 1 mil 15,625 250 1* Assumptions: 100 eggs/female, 50% sex ratio,

80% natural mortality.

Mating disruption: It is difficult toassess the level of control that can beexpected from mating disruption. Thelevel of suppression is dependent on thepopulation pressure within an orchard.As the pressure increases, the level ofcontrol can be expected to decrease.However, the use of mating disruptiondoes provide some suppression evenunder high-pressure situations and thatcould be critical to the success of aninsecticide-based program.

Organophosphates: Guthion remains theindustry standard for CM control. Thisinsecticide can be relied upon toconsistently provide 95+% control of asusceptible population in a four coverspray program (Fig. 8). However, asCM populations develop highertolerances to azinphos-methyl, the levelof control will decrease and additionalcover sprays or supplemental treatmentswill be needed.

Results from Imidan (phosmet) trialswere more variable than with Guthion(Fig. 8). On average, Imidan resulted incontrol near the critical limit of 90%.However, the range of suppression

dipped to a low of 75% in some tests.An insecticide program based solely onImidan as a Guthion replacement wouldlikely prove less stable in the long-term,especially if the CM population hadalready developed elevated tolerance forGuthion.


What level of control can be expected?

4 trials

Range 75-99%

Avg 91.8%(±5.6)

24.5 lbsImidan

32 trials

Range 85-100%

Avg 94.8% (±0.1)

22-3 lbsGuthion

Level of control# Apps/genRate/aChemical

Figure 8: Summaries of field trials usingorganophosphates to control codling moth inseason-long trials.


Softest organic products

50.0%3450 ml

45.8%3900 mlCarpovirusine

9 trials

Range 32-76%

Avg 52.9% (±5.7)

31%Oil



Spinosad (Entrust)

100, 95%6

77, 78,88%36 oz+1%Success

+oil

61, 61%36 fl oz

98%68 fl oz

78%38 fl oz

78%64 fl ozSuccess


Figure 9: Summaries of field trials usingorganically derived products to control codlingmoth in season-long trials.



12

Organically derived products: The levelof control that can be expected from theuse of horticultural oil varies dependingon the number of applications. Therange of suppression observed in a 6-spray program is 32-76% with anaverage of about 50% (Fig. 9). This is awide range of expected control and canbe influenced by the amount of injurythat develops in the second generation orfrom a late flight/3rd generation activity.Eggs laid after the last oil spray isapplied are not affected.

Carpovirusine used in a 6-spray programhas provided about 50% control with nodifference in control noted at the ratestested (Fig. 9). These data suggest thatthe treatment interval may be moreimportant than the rate. In other words,more frequent applications of the lowerrate might be needed to further reduceCM injury. We have limited experiencewith this product though it does look tohave some promise for our area.

Several tests with Success wereconducted using different rates andcombinations of oil (Fig. 9). A coupletreatment programs show exceptionalcontrol of CM with Success. These weretrials where Success was applied atweekly intervals for a total of 12applications at 8 fl oz/acre, or 12applications at 6 fl oz/acre incombination with oil. Both of theseprograms, if maintained for an entireseason, would be above label rates forthe active ingredient in the Entrustformulation. However, frequentapplications at lower rates incombination with oil would provideeffective control for a single generation.A grower must balance the need formore applications that use the season’sallotment of Success/Entrust in one

generation, or use the insecticide lessfrequently over the entire season.


Intrepid and Assail

90%33.4 fl ozWarrior

12 trials

Range 78-98%

Avg 85.8 (±2.0)

23.3 ozAssail

73, 73, 78%

Injured fruit

316 fl ozIntrepid


Figure 10: Summaries of field trials usingIntrepid, Assail and Warrior to control codlingmoth in season-long trials.

Intrepid applied at 14-day intervals for atotal of 6 applications consistentlyreduced fruit injury by 70-80% (Fig. 10).It is not uncommon for larvae that ingestIntrepid to enter the fruit and diesometime later. If larvae were dissectedout of the fruit and survival wasassessed, the actual impact on the CMpopulation may be somewhat greater.The level of CM control from Intrepidwas statistically the same when used asan ovicide or as a larvicide.

Assail performs consistently well whenused in a four cover spray program (Fig.10). The range of control andperformance of Assail is similar to whatwould be expected with Imidan. It is notlikely that a CM management programwould be based only on Assail forreasons detailed above, but certainly itcould be used to replace a specific OPspray without any notable loss inefficacy.

The synthetic pyrethroid, Warriorperformed well when applied at 14-dayintervals for a total of 6 applications(Fig. 10). However, the use of this



13

product is not encouraged except inspecific emergency situations aspyrethroids have historically beenimplicated with disruption of integratedmite control.

Possible causes of failureGaps in residual control: The level ofcontrol observed by a control programcan fall short of expectations for manyreasons (Fig 11). Shortened residualcontrol due to poor coverage orinsecticide resistance can leave gaps inthe program. If the gap in control occursafter the first cover spray (Fig. 11A) asmuch as 25% of the population couldhatch and be left uncontrolled in a one-week period. If the second cover sprayprovides only 14 days of residualactivity another 10% of the populationcould potentially be left uncontrolled.

The data presented in Table 3 shows thatregardless of the chemistry and mode ofaction, initial activity of an insecticide ishigh when coverage is not ideal, butresidual control is reduced. While thesedata are from a leafroller test theconcepts of coverage versus efficacy areimportant for CM as well. It should benoted that all of the insecticidespresented in Table 3 need to be ingestedto be effective.

An initial sign that a population isdeveloping resistance is shortenedresidual control from a particularinsecticide. It is reasonable to assumethat many CM populations inWashington have some level oftolerance to azinphos-methyl, thus a full21 days of residual control may not berealistic. Unfortunately, the actualamount of residual control fromazinphos-methyl is difficult to assess onan orchard-by-orchard basis.


0

5

10

15

20

25

30

0 50 100 200 300 400 500 600 700 800 900 1000 1100 1200DD from biofix

Predicted hatch

Any gaps in residual coveragePoor coverage, resistance

21 days 21 days

14 d 14 days


0

9

15

0 50 100 200 300 400 500 600 700 800 900 1000 1100 1200DD from biofix

Predicted hatch

21 days 21 days

Atypical flight activity

14 d 14 days

6

3

12


3rd Generation/Late Flight

0

5

10

15

20

25

30

1400 1500 1600 1700 1800 1900 2100 2200 2300 2400DD from biofix

14 d residual

Unprotected

10 Aug Predicted hatch

Figure 11: Possible sources of error due to gapsin residual control (A), atypical phenology (B)and 3rd generation (C). Expected control shownin red bars and observed control shown in green(A, B only).

Atypical phenology: It is not uncommonto observe CM population developmentthat varies from model predictions (Figs.11B-C). Developmental models aremathematical explanations of normal oraverage development. There are manyreasons that what really happens can



14

vary from model predictions, forexample:

• Immigration from an outsidesource (dirty neighbor)

• Introducing individuals into anorchard that are notdevelopmentally in-sync withnatives (e.g. bin piles)

• The more generations that occurin a season the less precisemodels work (e.g. 3rd CMgeneration)

• Insecticide use eliminates theearliest emerging individualsthereby selecting for a lateemerging population

• Choosing a mating disruptionproduct that stops releasingpheromone before secondgeneration is completed

Any combination of the events listedabove can result in a change to amanagement program that was plannedaround timing sprays with a model. Anyperiod of observed adult activity shouldbe treated as “real” and managedappropriately.

Atypical flights can constitute the largestpercentage of observed captures in someorchards and thus have the potential tocause the most injury. The sources oferror associated with residual controland unexpected adult activity can alllead to variable control results,especially if a grower depends on asingle control tactic. The most stableCM management program is one basedon a control strategy that will maintainpopulations at low levels using a varietyof tactics targeting as many life stages aspossible. A sound monitoring programis crucial if an IPM practitioner is tofully utilize the available tools.

Table 3: Residual control of leafroller by variousinsecticides in a leaf-disk bioassay, 1999.

Mortality- Days after trtInsecticide

CanopyLocation 7 d 14 d 21 d

Success Periphery 100 95 100Interior 100 95 80

B.t. Periphery 88 66 50Interior 71 41 34

Confirm Periphery 98 97 96Interior 100 100 75

B.t., Bacillus thuringiensis, organicallyregistered bacterial stomach poison.Confirm, growth regulator analog to Intrepid.

Documents

Codling Moth Management with New Insecticidesentomology.tfrec.wsu.edu/jfbhome/growerarticles/cm management with... · insecticides requires an understanding of ... (mainly in pear),