Insecticidal Alcaloid

8/10/2019 Insecticidal Alcaloid

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COOPERATIVE EXTENSION UNIVERSITY OF CALIFORN

FOR COMMERCIAL GROWERS

Summer 1989

CONTROL OF APHIDS ON ORNAMENTAL CROPS

JA Bethkq S.L. Veh, .tM. Garcia, andA4.P. ParrellaDepwtmentof Entomology, University ofCalifo* Rivd

Aphids have become increasinglyimportant pests in ornamental cropsduring the last few years. As aphids feed,honeydew is excreted, promoting thegrowth of black sooty mold which re-duces photosynthesis and the aestheticvalue of the crop. Feeding on youngfoliage can cause serious leaf distortionand stunting of growth. Aphids are alsoknown to transmit several plant viruses,making it imperative to control popula-tions. Due to parthenogenetic reproduc-tion (reproduction by unmated females)and the birth of live young, populations

Present address: Department o f Entomology,University of California, Davis

/co&NTs

paControl of aphids on Ornamental Crops .

Fumigation of Western Flower ThripsUsing Banana Bags (Polyethylene-D)During Simulated Shipment of CutFlowers .

Control of Algae on Greenhouse Walks .The Effectiveness of Hydrogels in

Container Plant Production is ReducedBy Fertilizer Salts .

build up very quickly, particularly in thecontrolled environment of a greenhouse.Adding to the problem, it is suspectedthat some aphids have begun to developresistance to organophosphate and car-bamate insecticides. For these reasons,controlling aphids is important, yet diffi-cult to accomplish.

As mentioned above, some species ofaphids have begun to show resistance tosome insecticides. It is therefore impor-tant to determine which aphid speciesone is dealing with before selecting anappropriate control (Vehrs et al. 1988).At the present time, a survey is beingconducted to identify the aphid pestsfound in California greenhouses on or-namental crops. Approximately tenspecies have been found thus far; how-ever, two species have been by far themost common. These are the greenpeach aphid, Mjzus persicae (Sulzer),and the cotton or melon aphid, Aphidgossypii Glover. Both of these species arefound attacking a wide variety of plantsfrom several different families and bothtransmit several different plant viruses.

Three insecticide screening trials havebeen conducted by the ornamentals proj-ect at U.C. Riverside in order to evaluatethe efficacy of different chemicals for thecontrol of aphids (Table 1). Some of the

compounds tested are new chemicalswhich have not yet been registered fouse in California and some are oldematerials which are being re-evaluated.

Trial I. The first trial wasconducted ina greenhouse at U.C. Riverside to evaluate the efficacy of four insecticidal trements against the melon aphid infestingchrysanthemums, Lkndranthema grandifloru Tzvelev. Each treatment, including a water control, was applied to techrysanthemum plants growing in 6 incpots under greenhouse conditions. Aone gallon B & G handsprayer was useto apply materials at 45 psi at a volumproportional to 100 gallons per acrPretreatment counts were taken beforeapplication and posttreatment countwere made at 4,10, and 15 days thereaf-ter. Evaluations were made by countingthe number of live aphids present on onrandomly selected marked leaf per planand on the terminal of each plant.

All treatments showed good results 4 and 10 days posttreatment (Tables and 3). At 15 days posttreatment, Mavriprovided the best control followed Rohm & Haas RH 7988 and Black Le

40. Safers Insecticidal Soap is a contacpoison; therefore, it was not expected give residual control. It did give goresults until after day 4. No phytotoxicitwas observed in any of the treatments.

The Unkenky of Wifomla, in complianra rrith the Civil Rights Ac t of 1 OS4 , Title lX of the Education Amendme nts of 1972, and the Rehabilitation Act of 1973, does no t dison the basis cd race, creed, religion, color, national origin, sex, or mental or physical handlcap In any of Its programs or activities, or with respect to any d its employment popmctica, of procedures. The Uniwrslty cl CalWomia doe s not dlscrlmlnata on the basisof ag e, ancestry, sexual orientation, marital status, citizenship, medical condition as dein section 12928 cd the Callfomia Gavernm -ant Code), nor because Individuals are disabled or Vietnam era veterans. Inquiries regarding this policy m ay bn directed to the DCNtka of Affirrnatlvs Actlon, Divlslon ol Agrlcuitum and Natuml tkxwce s, 300 Lakeside D rhre, Dakland, WWo mia 94612-3550, 415) 887-OO g7.

Unlvenity of California and U.S. Cupartment of Agrlculhrre cooperating.


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Table 1. Materials evaluated for aphid control.

Trade Name Manufacturer Common Name

Black Leaf 40 Black Leaf Products Nicotine SulfateDanitol Sumitomo FenpropathrinDursban Dow ChlotpyrifcsMavrick ZoecomSandoz FluvalinateOrthene Chevron AcephatePounce FMC Permethrin

RH 7988 Rohm & Haas Rohm St Haas Numbered CompoundSafers Soap Safer Agro-Chem Potassium Salt of a Fat ty AcidTalstar FMC BifenthtinXRD 473 Dow Insect Growth Regulator

Trial IL The second trial was alsoconducted in a greenhouse at U.C. Riv-erside to evaluate four separate insecti-cides and two tank mixtures for controlof the melon aphid on chrysanthemums.Each treatment and the water controlwas applied to four chrysanthemumplants growing in 6 inch pots undergreenhouse conditions as described inthe previous trial. Apretreatment countand three posttreatment counts after 5,10, and 15 days were made by countingthe live aphids on one terminal and oneleaf of each replicate.

All of the chemicals tested resulted ingood control through day 15 (Tables 4and 5). Danitol2.4EC, Pounce 3.2EC,Pounce and Orthene, and Dursban andPounce gave slightly better control thanDursban 50W or Orthene 75s alone.

Trial lIL The most recent trial wa sconducted at a commercial nursery inSan Diego County to evaluate the eff i-

cacy of treatments against the greenpeach aphid on field grown Shastadaisies, Chrysanthemum maximum Ram.Each treatment, including a water con-trol, was applied to four, randomly se-lected, twenty-four sections of groundbeds containing plants growing in a 0.5acre field on a north-facing slope. A 15liter backpack sprayer was used to applythe treatments at about 45 psi. Pretreat-ment counts were taken before applica-tion andposttreatments weremade after7,14, and 23 days. The total number oflive aphids were counted from ten ran-domly-selected terminals (young flowerspikes) in each twenty-foot section.

Beginning with the pretreatmentcount, it was noted that high numbers ofaphid parasites and predators were pres-ent in the field (Table 6). At the firstposttreatment count, numbers of liveaphids had already begun to decline evenon the control plants. By the last

posttreatment count, fe w if any livaphids were found on any of the terminals. Rohm and Haas compound RH7988 and Black Leaf 40 appeared tprovide the best control; however, nsignificant differences were found btween any of the treatments and thecontrol.

CONCLUSIONS

In these studies, the melon aphid(MA) was easier to control than thgreen peach aphid (GPA). Mavrik wgenerally effective against MA and inefective against GPA. This compound one of the safer pyrethroid insecticidefor both applicators and plants. However, there may be a problem with eyirritation with Mavrik and possibphytotoxicity problems on lilies. Nictine sulfate was effective in most triaagainst both aphid species. Although obotanic origin, this material is hightoxic (Category 1) and is very volatileShould the new worker protection standards go into effect, this product woulhave a mandatory 48 hour re-entry interval. Adding soap to the nicotine sulfatmay enhance its effectiveness (Parrella1988). Nicotine is generally safe oplants and open blooms, but problemshave been reported on violets, fernscertain chrysanthemum cultivars, anorchids. Care should be exercised whenusing this product on plants sensitive t

Table 2. Eff ica cy of selected insecticides against melon aphid,&is gosypii Table 3. Eff icacy of selected insecticides against melon aphid, Aphlgos@Glover, on chrysanthemum, Dena?anthcma grana?jlora Tzvelev. Glover, on chrysanthemum, Dendranthenta gradiifloa Tzvelev.

Mean Number of Aphids per Leaf* Mean Number of Aphids per Terminal*Rate per Rate per

Treatment 100 Gal Day 0 Day 4 Day 10 Day 15 Treatment 100 Gal Day 0 Day 4 Day 10 Day 15

Control 2.1 20.9, 7.5k3.9, 52.7 k15.2, 67.1 k13.7, Control 19.7 +5.9, 71.7 223.7, 183.9 k38.7,256.4 245.2

Safers Soap 2.0 Gal 0.9 kO.2, 5.9 3.0,s 32.8 &17.7,, 63.0 k14.8, Safers Soap 2.0 Gal 21.4 +5.8, 1.0 20.4,51% (AI) 51% (AI)

10.8 k3.6, 258.4 k42.9

Black Leaf 40 0.39 Gal 1.4 kO.5, 0.0 +O.O, 1.5 kO.7, 7.2 +lL$, BlackLeaf 400.39 Gal 21.2rt5.2, 0.0 +O.O, 1.1 kO.5, 8.440% (AI) 40% (AI)

28.6

Rohm & Haas 0.125 lb 1.3 +0.4, 0.0 kO.0, 0.1 +O.l, 5.3 -1-1.6, Rohm &Haas0.125 lb 21.5 k5.5, 0.1 +O.l, 0.7 kO.3, 14.5 k5RH 7988 4E WI RH 7988 4E (AI)

Mavrik 2FM 0.15 lb 0.8 +0.2, O.O+O.O, 0.0 kO.0, 0.8 +0.7, Mavrik2FM 0.15 lb 26.1 k5.1, 0.0 -cO.O, 0.0 20.0, 1.0 *WI WI

$10 plants per treatment; 1 leaf sampled per plant per date (the same leaf was 10 plants per treatment; a terminal sampled per plant per date (the terminal marked and sampled over time). Means followed by the same in a column are sampled over time). Means followed by the letter in a column are not signifinot significantly different (P=O.O5) DMRT. different (P=O.O5) DMRT.

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tobacco mosaic virus. Dursban andPounce,although not generally consid-ered good aphidicides, performed wellagainst MA

The new products tested n these rials(Danitol, Talstar, and RH 7988) mayoffer some hope in the future for aphidcontrol. Talstar has been registered onornamentals n mostof the U.S. or morethan two years; egistration is still pend-ing in California. The delay has been

causedby a request for additional resi-due data by the California Departmentof Food and Agriculture. A label forDanitol may come through in 1989withRH 7988 obtaining registration some-time in the 1990s.Acknowledgementshese studies were sup-ported, n part,by grants romthe CaliforniaState Florists Association, the California As-sociation of Nurserymen and the AmericanFloral Endowment.

REFERENCES

Parrella, M.P. 1988. Organic gardeninGreenhouse Manager 6:91,92,94-%

Vehrs, S.L., J.A. Bethke, J. Garcia, M.P. Parrella. 1988. Aphids: Comon Problems on Numerous Ornamentals. Calif. Florists MagaziJan. 15 pp.

FUMIGATION OF WESTERN FLOWER THRIPS USINGBANANA BAGS (POLYETHYLENE-D) DURING

SIMULATED SHIPMENT OF CUT FLOWERS

SteveA. T$9svoldFarm Adviror, Univ~ of California Cooperative Extension, Santa Gnu County

A. D. AilEa emion Entomoli~& Univ@ of CalijYomia, Riverside. -

Presently U. S. flowers are receivingpremium prices on the Japanesemarketrelative to domestic U. S. prices. Yetflower importation is restricted by theJapanese government, which demandsthat all plant material entering Japan befree of insects,either live or dead.

For California flower growers, con-trolling all of the insectson flower cropsisverydifficult. Western flower thrips, inparticular, is difficult to control becauseit feeds in protected areas,such as par-tially opened buds or unfolded leaves.This complicatescontrol due to the inac-cessibilityof thosehiding sites. Further-more, insecticidesused to control thripsare not completely effective due to resis-

tance and other factors.Thisstudyattempted todetermine theeffectivenessof controlling thrips duringstimulated shipment by wrapping theflowers with a commercially availablepolyethylene bag (banana bag) contain-ing 1% chlorpyrifos (Polyethylene-D).

F Chlorpyrifos is volatile and its fumesshould penetrate the flowers and kill thethrips.

MATERIALS AND METHODS

Experiment 1. A study to determinephytotoxicity of the fumigation trcat-ment during a simulated shipment wassetup. Three treatmentswere used: (1)Flowers wrapped in Polyethylene-D,boxed,and stored at approximately 1C;(2) Flowers without Polyethylene-Dboxed, and stored at approximately 1C;and (3) Flowers wrapped in Polyethyl-ene-D, boxed, and stored at room tem-perature (20C).

Each day, or three days,one flower ofeach variety was taken out of the boxes,examined for phytotoxicity, and placedin vases or observation. Eight varieties

of carnations (Improved New Pink Sim,Lena, Tango, Chianti, ImprovedWhite, Lareve, Lavender Lace, andVanessa), three varieties of roses(Riva, Sonia, and Bridal White) andthe gypsophila variety Bristol Fairywere used n the experiment.

Experiment 2 Thrips-infested Im-proved Red Sim carnations were har-

vested from a greenhouse. The averagenumber of thrips present before treament was determined from 20 floweselectedat random. In order to determine the effects of the fumigant, sixcarnations were wrapped in Polyethyene-D and placed in a flower box at approximately 1C. Another sixty carntions were wrapped in an ordinary polethylene dry-cleaning bag with ln inholes cut into it to increase air circultion (similar to the Polyethylenebags). These were also boxedand held atapproximately 1C.

Twenty flowers were removed ever24 hours for 3 days from each box anthrips in each lower were extractedand

counted. To count thrips, each flowewas emoved from the stemand the calywas emoved so the petals becamesepa-rated. The petals were placed in a specially designed thrips-separating can. A5-pound coffee canwas divided by a.wirmesh hat allowed thrips to be separatefrom the flower petals. A thrips irritaniso-butyl ketone forced the thrips off tpetals in one compartment of the can

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The thrips then could be collected in theother compartment, shaken out, andcounted on a white sheet of paper.

REsuLm

Experiment1. No phytotoxicity wasobserved throughout the experiment onany variety. Vase lives of refrigerator-stored fumigated and unfumigated flow-ers were identical, averaging 10 days orthe carnationsand gypsophila and 6 daysfor the roses.

Ehpeximent 2 Thrips counts are pre-sented n Tables 1 and 2.

Table 1. Mean number of thrips per carnationflower afte r 1,2, or 3 days of treatment.

Days ofTreatment Polyethylene-D Untreated

0 (precount) -- 3.05 --1 0.65 1.402 1.70 2.803 1.45 2.45

Table 2. Mean number of thrips per carnationflower over entire experiment.

Treatment Thrips numbers*Polyethylene-D 1.28 a

Untreated 2.20 b

*Treatments significantly diffe rent at the 1% levelusing L.S.D. mean separation.

DISCUSSION

Polyethylene-D fumigation duringrefrigeration reduced the numbers of

thrips present on carnation flowers, byapproximately 50%. Complete controlof thrips was not achieved under theseconditions possiblydue to the high thripsnumbers at the beginning of the experi-ment. It is conceivable that with lowernumbers of thrips, this technique mayprove more efficacious.

There are several merits of this ap-proach. First, there are no wet spraysinvolved or associated calibration and

mixing inconveniences. Second, he ac- have traditionally caused phytotoxictive ingredient, chlorpyrifos (Dursban), to roses. Lastly, the cut flowers cais registered for a variety of pestson a wrappedwith the Polyethylene-D bagsatwide range of floricultural crops. Third, the time of boxing, thuseliminating cosno phytotoxicity was observed on se- for additional applications and handllected rose varieties. This is significantsinceother formulations of chlorpyrifos

Note: Polyethylene-D bags presently are. not regitered for use on flower crops.

CONTROL OF ALGAE ONGREENHOUSE WALKS

Robert D. Raabe and Joseph H. HurlimunnDepartment of PIant Pathology, Univ~ of California, Berkeley

DelbtiFamhumFarm Advisoc Univ~ of Califomiu Cooperative Exttin,

A??dbrcounty

In greenhouses requiring reducedlight and high moisture for growing cer-tain typesof plants, algae can be a prob-lem on greenhouse walks, walls andsometimes on the glass. On walks,growth canbeso abundant that there is adanger of slipping. Becauseof this, anexperimentwasdone on an orchidgreen-house near Watsonville, CA, where al-gae were a problem.

many of the walks were completely cov-

The alga involved, Stic~0c0ccus ub-&Y (Kutz.) Klerch., was so abundant

tion. There wassomecontrol at the 15 mconcentration, but it was not adequatTwo months after thelast application, nalgae had grown on the walks treatewith the higher concentration.

amount needed to give control.

Under conditions very favorable fthe growth of algae,control should resufrom application of Physan@nce everytwo monthsat the concentration of 30 m(2 tablespoons) per gallon. Longer intervals might be effective and appliction with a sprayer might reduce th

ered. Two concentrations of the quater-nary ammonium compound Physan@were applied 3 times at monthly inter-vals. Sectionsof walkway 30 nchesby 20,feet were treated with 2 gallons appliedto runoff using a sprinkling can. Concen-trations included 15 ml and 30 ml Phy-San@er gallon.

During the experiment, excellentcon-trolwas observed at the 30 ml concentra-

r \moWa& N-e is published quarterlyby the Department of Environmental Hotticulture, Unive rsity o f California, Davis. We argrateful to the San Diego County Flower Association and the Monterey Bay Flower Growerfor their generous financial support, which partially defrayed the cost of publication.

Richard EvansEditorL

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THE EFFE(TIVENESS OF HYDROGELS IN CONTAINERy PLANT PRODUCTION IS REDUCED BY FERTILIZER SALT

Rkhani K Evans and Ihiu S&toDepament of Enti rammtal Horticubq Univ~ of California, Davis

Daniel c BowmunDepa- of Pht Science, Univ~ of New&, Rem

Hydrophilic polymers first becameavailable to the nursery trade in the early197Os, and interest in their application tocontainer plant production has waxedand waned more than once since then.These amendments are receiving a lot ofattention once again as suppliers pro-mote the purported advantages of hydro-philic polymer addition: decreased wa-ter use, which is particularly attractiveduring a drought, and less product lossfrom infrequent watering, which is moreimportant now that large retail chainsare major outlets for nursery products.Unfortunately, growers seeking infor-mation about the effectiveness of hydro-philic polymers have encounter conflict-ing information from salesmen and hor-ticulturists alike.

It has been suggested that hydrogelsmay be useful as a soil amendment toimprove water-holding capacity becausethey can hold up to 1500 times theirweight in water. There have been severalreports by researchers indicating bene-fits from hydrogels. Additions of gel to apeat:perlite mix reduced water stress andincreased time to wilt in zinnias.In someother studies, researchers found that thefrequency and total amount of irrigationcould be reduced by incorporating gels inthe potting mix. However, other reportshave shown little or no benefit from gels

added to potting mixes at recommendedrates, and a recent study of gel effects onwater stress in tall fescue concluded thatgels were not effective unless added atmore than 80 times the recommendedrate.

The absence of benefit from gels insome of these studies may be due to theinhibition of gel hydration by salts dis-solved in the irrigation water or fertiliz-ers. For example, growth of Ligusmm

lucidurn in a gel-amended mix was nega-tively affected by increased fertilizerrates. In addition, there have been sev-eral reports describing the inhibition of

These results show that fertilizer solu-tions, such as those used in the green-

gel hydration in the presence of salt solu-

house and container nursery industry,might restrict the potential benefit of

tions.

hydrogel as an amendment. We haveinvestigated the effec ts of various fertil-izer salts, at concentrations commonlyused in container plant production, onwater absorption by three poly-acrylamide hydrophilic gels. In addition,we examined the effec t of fertilizer saltsand gel amendment on the physicalproperties of three typical containermedia: a redwood sawdust:sand (2:l byvolume) mix typical of those used inwoody plant nurseries, a redwoodsawdust:peat:sand (1:l:l by volume) mix

typical of a heavy greenhouse pottingmix, and a peat:perlite (2~1 by volume)mix typical of a light greenhouse pot-

Effect of fertilizer salts on water ab-

ting mix. Finally, we report the effects of

sorption by gels. Dry gels were allowedto absorb solutions of several com-

gel addition on the growth and time to

monly-used fertilizers for 24 hours, afterwhich the excess solution was removed

wilt of potted chtysanthemums.

and the hydrated gels were weighed todetermine moisture absorbed. Fertilizersalts substantially reduced absorption bythe gels (Fig. 1). At a concentration of 20meq l-l, which is typically found in manycommercial fertilizer solutions, the gelsabsorbed only 114 or less of the amountabsorbed in deionized water. Absorp-tion in fertilizer solutions containing 20meq 1-l of either calcium (Ca2+) or mag-nesium (Mg2+) was reduced to less than10% of that in deionized water. In con-

Urea concentration (mM)0 5 10 15 20

I-v-v- V ;I O-OKN03

V-VKH2P04A-ANH4N03A- A(NH&=4-OCO(NO3)2

O--OCa(H2PO4)2=WdNO&q - gs04V-VUrea

00 5 10 15 20

Solt concentration (meq I-)

Fig. 1. Effec t of fertilizers on hydration of a hydrophilic polyacrylamide gel. The upper group of cushows the response to monovalent cations and the upper group shows the response to divalent cations.

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Hoogland Solution Strength

A-AGd Bo-OGOI c

0.0 0.5 1.0 1.5 2.0

ECsolutiondS m-1Fig. 2. Effec t of a complete Hoaglands nutrientsolution on gel hydration.

trast, the uncharged solute, urea, did notreduce absorption at any concentrationtested. When gels were allowed to ab-sorb a complete nutrient solution(Hoaglands solution), the reduction inabsorption was almost identical to thatin the presence in Ca2+ or Mg2+ at similarconcentrations (Fig. 2).

To determine whether the water ab-sorption of salt-inhibited gels could berestored by clear irrigation, we examined

500

400

T 300

WI; 200

o, 100

E 05 500'Zp? 400

s 300

200

100

CaPJQ2

2nd 3rd 4thRime. Rim Rinm

Fig. 3. Reversa l of salt-inhibition of gel hydrationby sequential deionized water rinses Gels wereinitially hydrated in 20 meq l-t Ca(NOd2 (uppergraph) or KNO, (lower graph).

Table 1. Physica l properties of gel-amended redwood sawdusnsand (21) medium,irrigated with deionized water or a fertilizer solution.

Total Air-tilled Container Hz0 Content BulkPorosityz Porosity ~PaW at 100 cm Density

Treatment (vol %) (-Jo1%6) (vol I) (vol %) (g cme3)

Control- Fertilizer 74.6 d 21.1 a 53.5 cd 19.1 a .60 a+ Fertilizer 74.4 c 19.8 a 54.6 c 18.9 a .61 a

lxGel(2 lb/cu yd)- Fertilizer 77.4 b 17.6 b 59.8 b 37.3 d .54 b+ Fertilizer 74.3 c 21.5 a 52.8 d 21.9 a .61 a

2xGel(4 Ib/cu yd)- Fertilizer 78.5 a 16.8 b 61.7 a 29.7 c .51 c+ Fertilizer 75.0 c 20.6 a 54.5 cd 26.4 b .59 a

xData are means of three replications.YMeans followed by the same letter within a column are not significantly different, 0.05

the permanence of the salt effect on gelhydration. When gels which had been

hydrated in 20 meq I- KNO, were rinsedrepeatedly in deionized water, absorp-tionafter the third rinsewas greater thanthe maximum following hydration indeionized water (Fig. 3). However, ab-sorption by gels which had been hydratedin Ca(NOJ, could be restored to only28% of full absorption capacity, evenafter four rinses.

EZffectoffertilizersaltsandgelamend-ment on the physical properties of aredwood sawdustsand potting mix. Acontainer mix typical of those used in thewoody nursery industry was preparedfrom redwood sawdust and sand mixed ina ratio of 2:l. The mixwas divided in two,with half amended with dolomite, super-

phosphate, potassium nitrate, and Mcromax. The other half received

chemical amendments. A hydrophiligel was mixed into both the amended aunamended mixes at rates of 0,2 (manufacturers recommended rate), and 4 lper cubic yard. Columns 13 cm de(between the height of a 6 pot andgallon container) were filled with eacthe mixes. The chemically-amended mwas irrigated with a fertilizer solutiand the unamended mix wa s irrigatewith deionized water, after which physical properties of the mixes wedetermined by standard methods. Addtion of gel altered the physical propertiof the mix that received no fertilize(Table 1). Total porosity and containecapacity increased slightly, and air-fille

Table 2. Effec t of gel amendment on the physical properties of U.C. mix andpeatperlite.

Treatment

Total Air-filled Container Bulk AvailablePorosity Porosity Capacity Density water(vol %) (vol %) (~01%) (g cmS3) (vol a)

Ib/cu yd024

UC Mix

78.6 12.7 65.9 0.50 53.080.5 12.2 68.3 0.45 54.981.0 14.5 66.5 0.46 54.4

lb/cu yd024

92.993.393.5

Peat:Perlite

29.3 63.6 0.14 53.027.0 66.3 0.13 55.422.0 71.5 0.13 54.9

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Table 3. Effect of hydrophilic gel amendment ondays to wilting of chtysanthemum kept in a green-

p house or in simulated supermarket conditions.Plants were irrigated to container capacity withHoaglands solution, then water was withheld untilshoot tips wilted.

Rate(lb/cu yd) UC Mix Peat-Perlite

Greenhouse

0 1.12 1.132 1.15 1.134 1.18 1.16

0 2.95 2.962 3.00 2.984 3.01 3.05

Means within a treatment group (greenhouse orsupermarket) were not significantly different(P=O.O5).

porosity decreased slightly with gel addi-tions. When fertilizers were present,however, gels did not affect total or air-filled porosities. The amount of water

p held at 100 cm tension increased sub-stantiallywithgeladditionin theabsenceof fertilizers. In contrast, there was ittleor no increase in the presence of fertiliz-ers.

Effect of gel addition on the physicalproperties of two greenhouse pottingmixes. Two greenhouse potting mixeswere prepared, one a U.C. mix contain-ing sphagnum peat, redwood sawdust,and sand in equal volumes, and the othercontaining sphagnum peat and perlitemixed in a ration of 2:l. Both receivedstandard chemical amendments (dolo-mite, calcium carbonate, super-phosphate, potassium nitrate, andMicromaP) and 0, 2 (manufacturersrecommended rate), or 4 lbs per cubicyard of a hydrophilic gel. The mixes were

wetted with a fertilizer solution to allowthe gels to hydrate, then columns 12 cmdeep (typical of the height of a mix in a 6pot) were filled with each of the mixesand the physical properties were deter-mined. The physical properties of theU.C. mix were not significantly affected

F by gel addition, whereas gel addition tothe peat:perlite mix increased the con-tainer capacity and decreased the air-filled porosity (Table 2).

Effect of gel addition on availablewater and on time to wilt and yield ofchrysanthemum. Rooted cuttings ofBright Golden Anne chrysanthemumwere planted, three cuttings per pot, in 6pots containing either U.C. mix orpeat:perlite and 0, 2, or 4 lbs per cubicyard of a hydrophilic gel. The plants werewateredasneededwithacompletenutri-ent solution and grown under vegetativeconditions, without growth regulatortreatment, for 6 weeks. At the end of thesixth week, a tensiometer was placed ineach container. The pots were irrigatedto container capacity, then irrigation waswithheld until the shoot tips began towilt. The pots were then leached repeat-edly with deionized water, moved to aroom which simulated supermarketconditions, and allowed to wilt again.Soil moisture tension and water lossfrom the mixes wa s measured until wiltoccurred. Gel addition did not affect theamount of available water in either mix(Table 2) and did not modify the mois-ture release of the mixes (Fig. 4). Simi-larly, the time to wilt in the greenhouseor the keeping room was unaffected bygel addition (Table 3), and the crop yieldwas similar in each treatment (Table 4).

Conclusions. The results presentedhere indicate that fertilizer salts dramati-cally reduce absorption by hydrophilicpolyacrylamide gels. Divalent cations(Ca*+ and Mg*+) dominate the effect offertilizers on gel hydration. These ionsmay lock the polymer in place, restrict-ing expansion (and thus water absorp-tion). Clearwatering does not overcomethe inhibition of absorption caused byfertilizers containing calcium or magne-sium.

Table 4. Eff ect of hydrophilic gel amend-ment on fresh weight (g) of chrysyan-themum.

Rate(lb/cu yd) UC Mix Peat-Perlite

0 317 3152 306 3144 297 292

Means were not significantly different(P=O.O5).

0.6

3,g 0.3

-z

jz 0.2

E 0.1

g0.0

2aI 0.7

T

2 0.6

klIi 0.53

0.4

..

*A q

b 00 . .0

_ Peat:perlitet q

0

IOel mtaOfa m-3,

/ 0.. 0

.v. 1.2

-9.

IO. 2.4

Flower & Nursery Report Summer 1989

0.3 - q a .0.2 -

5. l .*p

I

o., _ U.C. mixa ; :.

0.0 10 5 10 15 20 25

Tension kPa)

Fig. 4. Effec t of gel amendment on the moisturerelease of U.C. mix and pcatperlite.

In the absence of fertilizer salts, geladdition altered the physical propertiesof the redwood sawdust:sand mix. In thatmix there was a higher moisture contentat 100 cm soil moisture tension when gelwa s present, indicating that a substantialamount of gel-absorbed water is retainedwhile the bulk of the potting mix driesHowever, this increase in moisture con-tent occurred only in the absence of fer-tilizer salts. Since commercial green-house and nursery production dependson high fertility, it is unlikely that geadditions would improve the moisture

holding capacity, yield, or time to wiltunder most nursery conditions.

Acknowledgement. The authors gratefu lly acknowledge the skillful technical assistance of Ken-dra West.

7


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Dr. Fkhard Evans, editorEnvironmental Horticulture ExtensionUniversity of California, Dais

Cooperative ExtensionU.S. Department of AgricuttureUniversity of CaliimiaBerkeley, CA 94720

Penally for Private use: $300 I

Mail ID: 9396

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