Comprehensive Research on Strawberries Annual Report

Comprehensive Research on Strawberries

Annual Report

February 1, 1985 - Oanuary 31, 1986

Proiect Title: Heliothfsdetectionand controlinstrawberries

Pro_ect Leader and Princioa! U.C. Investigators:

3ohn T. Trumble, Project Leader Department of Entomology University of California, Riverside

Cooperators:

V. Voth W. Wiesenborn T. PerrJng Department of Pomology Dept. of Entomology Dept, of Entomology Univ. Calif. Davis Univ. Calif. Riverside Univ. Calif. Riverside

Level of 1986 Funding: $i5,000

Obiective$ and Experlment;_ Conducted to Accomollsh Ob iectives:

OB$ECTIVE_:

I. Detectionand Sampling A. Determine if pheromone traps can be used to predict outbreaks of Heliothis species. B. Document critical biology, ie. How, long is the period between egg deposition and larval penetration Into the berry? C. Develop a sampling plan for detection of Hello]his eggs on strawberries.

II. Chemical Trials A. Evaluation of "standard chemicals" (methomyl, dibrom, and carbaryt) B. Evaluate efficacy of other promising compounds, including permethrln, which has proven effective for Heliothis control on other crops, and FMC 54800, a promising compound which may also provide mite control.

EX PERIMENTAL PROCEDURES:

I. Detection and sampling studies.

Pheromone traps ('Texas' type) were placed in commercial and experimental strawberry fields in Orange County, California. The traps were checked weekly for adult Heliothis zea (Boddie) from 5anuary 1984 through 3uno 1984. On each date the traps were monitored, we counted the number of _H. ze_ eggs on ten plants adjacent to every trap (approximately 100 plants per week). Tomato frultworm counts In traps were high, but egg counts were tow. Additional studies using caged

56 moths are planned for the spring of 1987 to determine; J) where on the plants the eggs are deposited and, 2) how long is the period between oviposition and penetration of the fruit.

From 3anuary 1986 through Oune of 1986 pheromone traps were monitored twice a week. Counts of eggs were made in adjacent corn fields to determine how the attractiveness of corn varied with growth stage. The availability and planting dates for nearby corn fields were provided by the Irvine Company. Along with the first year's data, the trap catches were matched to major weather patterns to determine if pheromone traps could be used to predict outbreaks in strawberries.

II. Chemical Trials.

The primary purpose of this research was to generate information necessary for registration of new compounds for controlling Heliothis zea. In this study, an IPM approach was used to provide data on the impact of pesticides on the entire system, rather than just the target species. Groups responsible for registration have given strong consideration to registering new compounds when data demonstrates that currently registered pesticides wilt: J) cause outbreaks of a non-target pest which require use of additional pesticides, 2) damage plant productivity through reductions in photosynthesis or, 3) be unsuitable for use in a resistance management program. The experiments reported here were designed to determine the impact of both registered and unregistered compounds with potential for Heliothis zea control on populations of two-spotted spidermites.

Experimental deCgr_ - The test consisted of ten treatments including a control. Each treatment was replicated four times in a randomized complete block design. Individual replicates were two-row beds which were 30 feet long. All pesticides were applied on alternate weeks from March 5 through May 28 (total of seven applications). Actual dates of applications were: March 5 and 19, April 2, 16 and 30, May 14 and 28.

ADDlication Eouiomenf; - The sprayer was operated at 150 PSI. As plant height and foliage density increased, nozzles varied from 2-4 per row and carrier (water) was i 00 gal/acre unless specified. Disc-type nozzles incorporated D2 or D3 orifice disks, #23 cores, and 50 mesh screens. Ail treatments except Abamectin included 0.04% spreader-sticker (Leaf Act 80A).

Comoounds test_c_; Chemical Rate lb ai/acre Suoolier

FMC 54800 (Brigade) 2E 0.05 FMC FMC 54800 (Brigade) 2E 0.1 FMC Dibrom(Naled)8E J.0 Chevron Permethrtn (Ambush)2E 0.2 ICI Carbaryl (Sevin)80WP 2.0 UnionCarbide Methomyi (Nudrin) 1.8L 0.9 Shell Avermectin Bi (Abamectin) 0.02 Merck & Co. Avermectin BI (Abamectin) 0.02 (in 50 gal/ac) Merck & Co. Avermectin Bi (Abamectin) 0.02 (+ 0.1% old Merck & Co.

57 The majorarthropodpestsofstrawberrieswere evaluatedasfollows:

Spidelrmit;e_: Evaluation was based on percentage of plants infested on the highest trifoliate on each plant for ten plants/replicate every week (40 per treatment per week). Data were collected every other week from Mar Il through 3une 2. A_hids: Aphid counts were collected at the same times as the spidermite data, but percentage of plants Infested was based on the presence or absence of aphids on the oldest trifoliate, Again, ten randomly selected plants were sampled per replicate every week. B_neficiels: Numbers of beneficial insects were recorded from the highest and oldest trifoliates on the same dates and from the same plants as for the aphids. Ph_0toxicitv: Photosynthesis and stomatal conductance measurements were made with the LJ-Cor 6000 between Mar 11 and May 22 (see Tables 6A and 6B for actual dates).

Yield data were collected (all berries in each replicate) on the same dates as the mite counts. The numbers and weight of fruit from each of the four replicates per treatment were recorded.

All data were analyzed using the Proc GLM procedure and Duncan's multiple range test available from Statistical Analysis Systems.

Laboratory Trials For Ovicida] Efficacy: Insecticides were tested for ovicidal activity against corn earworm eggs ovipostted on excised strawberry leaves. Eighteen strawberry leaves with petioles in water were placed for 12 hours in a cage containing 30 male and 30 female corn earworm adults. Randoml y selected leaves were dipped in 400 m] of insecticide 30 hours following the oviposition period. Each leaf was an experimental unit; there were three replications. Insecticideconcentrationswere basedon 100 gat/acre.Aftertheinsecticidedried, 15 fertile(ringed)eggsfrom each leafwere isolatedby placingcutpiecesoffresh leafeach with one eggon moistcellucottoninuncoveredone cz plasiccups.Eggs were keptat 27+_I C andevaluatedforhatching96 hoursafterovlposition.

Summary of 1986 Research Accomplishments:

I. Detection and s_molirlq.

The results of the pheromone trapping study were similar to those presented in the previous annLralreport. The first fitght of adult H. zea were detected at low levels early in 1986, increased through March and peaked at 60+ moths per trap in April. The flight then deciined rapidly, demonstrating a strong periodicity which clearly defines a new generation. By early May, the next series of flights had begun. Although this flight also reached approximately 60 moths per trap, the majority of adult H. z_ were migrating to the neighboring corn fields which were increasing in attractiveness. Although the fifth flight in June appeared to be the smallest, there were many _H. z_8 present in the area, but the vast fnajority of these insects were congregating in the corn. Thus, the dynamics of intercrop movements plays an important role in determining if H. zea infestations will

58 occur in strawberries. This aspect of our research will be studied again next year, to determine if this effect occurs regularly.

The pheromone trapping data have been related to major weather patternsWhen combined with weather data on wind patterns and temperatures at heights favored by _H. zee, the following conclusions were made: 1) the adult moths were migrating on winds occurring at 850 millibars (mb) pressure, 2) moths aggregated at 850 mb when temperature inversions were present, and 3) wind direction and temperature were favorable for migration when a) Santa Ana winds began t_ decay, b) an onshore flow caused a weather pattern known as the Catalina Eddy to develop, or c) storms off the coast of Mexico generate stong winds from the south. A detailed analysis of weather patterns responsible for migratory movements will be presented in the final report for this project in 1987.

The biology of _H.ze8 on strawberries is currently under investigation. A laboratory colony has been established at U.C. Riverside, and the numbers of insects are being increased. We anticipate continuing and completing the detailed biology studies during 1987.

II.Chemi6¢ tri2]s - Fi_]¢.

The effects of the chemicals tested on populations of spidermites and aphids are presented in tables 1 and 2. Numbers of beneficials were too low to allow statistical seperation of means, so no table has been presented. Influence of pesticide aoplications on yield, including number of fruit per replicate, harvest weight, and average weight per fruit, are presented in tables 3, 4 and 5, respectively. The phytotoxic effects of pesticide application, as measured by photosynthesis rates and stomatal resistance, are presented in table 6.

Arthropod control: The effects of the chemicals tested on populations of spidermites are presented in table 1. Brigade and Abamecttn treatments provided the best control of spidermites (two spotted spidermIte, Tetranvchus urticae). The Abamectin treatments incorporating 0.1% oil or using only 50 gallons of carrier per acre were generally better than Abamectln at 100 gal/acre. Methomyl, naled and carbaryl applications generated spidermite populations which were equal to or greater than those in the control plots. Permethrin offered some population reduction Initially, but provided little control after March 2z,. In spite of high densities of aphids at the beginning of the trial, all pesticides significantly and rapidly reduced populations. The primary species was ChaetosiDhon fragaefolii (Cockerell), the strawberry aphid, but Myzu_ persicae (Sulzer) and Aphi_ oosswii Glover were also present. The control plots tended to have more beneficial insects than any of the pesticide treatments, but numbers of beneflcials were low throughout the trial, and statistical seperatton between chemical treatments was not possible.

Yield and phytotoxlclty effects were clearly associated. Brigade treated plots had the highest photosynthetic rates and lowest stomatal resistance (ie. resistance to air movement into leaf), followed closely by permethrin-treated relicates. All other treatments resulted in plots with fewer fruit, lower harvest weights, and

59 smaller fruit over the course of the season. This was probably due, in part, to the reductions in photosynthesis and increases in stomatal conductance caused by either a sub-visual phytotoxlc effect or the cummulative impact of spidermite feeding. Phytotoxicity was also visually evident: burning of both leaves and fruit were recorded in the naled-treated plots. Note: naled is not recommended by the manufacturer for use at temperatures above 80 F. No phytotoxicity was observed for any of the other insecti_des tested.

Please note, variation in photosynthesis or yield data from week to week within a treatment was expected to occur asenvironmental conditions changed. Also, the yields obtained during the latter portion of the season were affected not only by pesticide induced phytotoxicity, but by cummulative spidermite damage as welt.

Laboratory tests of ovicids] efficacy:. In managing corn earworm populations on strawberries, inflicting mortality during the egg stage will be a valuable control strategy. In these tests, the pyrethroids appear to be the most useful in that they provided 100% suppression. Although Lannate provided complete control as welt, the usefullness of this chemical would be reduced by limitations placed on growers by processors. The other compounds in this test, which also are registered for _H.Z_ on strawberries, provided significantly less control. Data from this study have been presented in Table 7.

Publications or RePorts: In the past few years, the Strawberry Advisory Board has supported Dr. V. Voth, who has cooperated with me to produce a variety of publications of Interest to the strawberry industry in California. Some of these publications are listed below.

Trumbie, 3. T. E. R. Oatman and V. Voth. 1983. Development and estimation of aphid populations Infesting annual winter plantings of strawberries in California. 3ournal of Economic Entomology 76: 496-501.

Trumbte, 3. T, E. R. Oatman and V. Voth. 1983. Temporal variation in the spatial dis_rsion patterns of aphids infesting strawberries. Environmental Entomology 12: 595 - 598.

Trumble, 3. T., E. R. Oatman and V. Voth. 1983. Thresholds and sampling for aphids in strawberries. California Agriculture 37 (11 & 12): 20-21.

Oatman, E. R, O. T. Trumble and V. Voth. 1983. Composition and relative abundance of parasites associated with aphid populations on strawberry in southern California. Environmental Entomology 12:1714- 17i 7.

Trumble, 3. T, H. Nakakihara and V. Voth. 1984. Development and evaluation of a wax immersion technique designed for studies of spidermite population dynamics on strawberries. Oournal of Economic Entomology 77: 262-264.

Carson, W., H. Nakakihara, O. Trumble and V. Voth. 1986. Arthropod control and chemical phytotoxJcity in strawberries, 1985. Insecticide and Acariclde Tests i I: 90.

6O Table1. Effectsof pesticideons two-spottespld dermltesIn Strawberries.

Treatment* MeanPercentPlantsInfestedonHlohestTrlfolla_** &lbAVac MarII Mai'17_ Mar3] Apr7 Apr14Apl;'22 Apr28.May5 May12May19May27,June2

Controi 50abc80ab 944 100a 100a 100a 100a 100a 100a 100a 100a 100a 100a

Methomyl 70ab 904 100a 100a 100a 100a 100a 100a 100a 100a 100a 100a 100a 0.9

Naled 50abc70abc 954 100a 90ab100a 100a 100a 100a 100a 100a 100a 100a 1.0

CarbaryI 754 854b 100a 954 954 100a 100a 100a 100a 100a 100a 100a 90ab 1.5

Permethrln 45abc 754b 80ab 100a 954 100a 100a 100a 90ab 100a 100a 100a 854b o, 0.2

Abamectln 35bcd40bcd 40cd 100a 75abc100a 954 954b 854b 55b 65bc 70b 40cd 0.02

Abamectln15cd 30cd 65bc 804 65bc 65b 804 75bc 50e 60b 70b 55b 80ab 0.02+ .1%oi1

Abamectln35bcd2od 60bo100a 90ab 854b 954 650 75b 75b 50cd 50b 10d 0.02in50gal/ac

FMC548005.0d 65abc 60bc 904 55c 80b 60b 954b 20d 60b 45d 70b 60bc 0.05

FMC5480015cd 20d 15d 55b 15d 35c 25c 60c 20d 20c 904 45b 15d 0,l 0 * AlltreatmentsapplledIn100gal/acunlessspeclfled. **Means In columns followed by the same letter are not significantly different al; P<0.05 (DNMRT). Analysis prior to conversion to percentages. Table 2. Impact of pesticides on aphids in Strawberries.

Treatment* M_Bn Pergent Plant_ Infeste_ on Olde¢; Trif0]i_** & lb AL/ac March Il March 17 March 24 March 3l April 7

Cont roi 60.0a 25.0a 15.0a 35.0a 15.0a

Methomyl 0.0c 10.0ab 0.0b 0.(7o 0.0b 0.9

Naled 0.0c 10.0ab 0.0b 5.0b 0.0b 1.0

Carbaryl l O.Obc 15.0ab O.Ob O.Ob O.Ob 1.5

Permethrin 5.0c l 0.0ab 0.0b 0.0b 0.0b 0.2

Aba me ct in 30.0b 5.0ab Q,0b 0.0b 0.0b 0.02

Abamectin 15.0bc I 0.0ab 0.0b 5.0b 0.0b 0.02 + .l% oil

Aba m ect tn 15.0bc 10.0ab 0.0b 0.0b 5.0b 0.02 in 50 gal/ac

FMC 54800 5.0c 0.0b 0.0b 0.0b 0.0b 0.05

FMC 54800 5.0c 0.0b 0.0b 0.0b 0.0b 0.]0 * All treatments applied in 100 gal/ac unless specified. **Means in columns followedby the same letterare not significantly differentat P<0.05 (DNMFRT). Analysispriorto conversionto percentages.

62 Table3. Effectsof pesticideons numberof StrawberryFruit produced.

Treatment_ MeanNumberofStrawberryFruitP1'0dufed"* &lbAI/ac Mar24 Mar31 Apr7 Apr14 Apr22 Ap_28 May5 May:12 May19 May27 June2

Controi 42.5a 90.Sab 81.3c 67.3de 78.8ab 67.5bc 38.8cd 34.0cd 17.8c 27.0b 32.5b

Methomyl30.8a 83.0b 79.5c63.3e 71.5b 67.5bc37.5d 37.0cd20.3c 29.3b 26.5b 0.9

Naled 36.5a 94.8ab 91.0bc64.3e 75.3b 56.3c /46.0bcd42.8bcd20.0c 40.5b 46.3b 1.0

Carbaryl 35.5a 88.3ab 74.8c 69.8cde78.3ab 62.8bc 37.8d 24.8d 17.3c 36.5b 27.8b 1.5

Permethrln/40.8a 93.0ab 91.Obc76.0bcde90.3ab 81.3abc56.Sabcd51.8abc29.3bd c 55.8b 52.8b a, 0.2

Abameclln 42.3a 98.0ab 112.5a81.8abcde105.3ab94.8abc58.Sabc6d4.5abc39.8abc84.5a 89.8a 0.02

Abamectln32.8a !I 1.3a 106ab96.0ab 100.8ab113.8a 78.3a 67.0abc45.5ab 91.5a 90.8a ·0.02+ ,1%ell

Abamectln43.3a 99.3ab 116.5a89.5abc106.Sab99.8ab 59.5abcd67.0abc47.8ab 99.0a 100.3a 0.02In50gal/ac

FMC54800 32.8a 105.3ab120.3a101.0a 106.Sab104.8ab67.3abc71.Sab37.8abc84.0a 99.5a 0.05

FMC54800 32.3a 110.0a 116.5a86.5abcd117.0a 101.0ab69.0ab83.0a 54.0a 102.0a 95.5a 0,10 * AiltreatmentsappliedIn 100gal/acunlessspeclfled. *MeansIncolumnsfollowedbythesameletterarenotsignificantlydifferentat P<0.05(DNMRT). Table4. Effectsof pesticideons yieldor strawberryfruit perreplicate.

Treatment* MeanYield(grams)orStrawberryFruitP_rReplicate** &lbAl/aC Mar3l Apr7 Apr]4 A_ Apr28 May5 May]2 May19 May27 Jun_2

Control 2491bcd2076ab1341bcc d1059a 999bcd 5lIbc 4lScd 270cd 330b 441b

Methomyl 2465bcd168:2bc117Id 1105a lOl3bcd 494bc 507cd 274cd 383b 353b 0.9

Naled 2496bcd1865bc1193cd 1092a 941cd 726abc540cd 274cd 552b 64lb l.O

Carbaryl 2199d 1621c 1559abcd1128a 8a0d 429c 290d 242d 443b 391b 1.5 o, Permethrln2304cd187YDc1462abc1d430a 1340abcd716abc699bcd 479bcd 792b 826b _' 0.2

Abamectln 2806abc221labc 1628abcd1494a 1674abcd990abc997abc 665abcd1391a 1474a 0.02

Abamectln 2927ab2242ab1846a 1625a 1998a ]239a 947abc 817ab 1549a 1508a 0.02 + .1_ oi1

Abamectln 2878ab2479a 1789ab 1725a 1772abc1001abc1175ab 766ab 160la 1720a 0.02in 50gal/ac

FMC54800 3009ab2483a 1910a 1998a 1873ab 1159a 1168ab 707abc 1461a 1798a 0.05

FMC54800 3108a 2580a 1668abc1769a 1968a l11lab 1355a 97/_a 1741a 1650a 0,10 * All treatmentsappliedIn100gal/acunlessspecifiedWeights; werenotsignificantlydlfl'erentonMarch24(DNMRT). **MeansIncolumnfolloweds bythesameletterarenotslgnlfIcantlydifferentat P<0.05(DNMRT). Table5. Effectsof pesticidesonaverageweightof strawberryfruit produced.

Treatment* MeanAverageWeight(grams)of StrawberryFruitProduced** &lbAl/ac Mar24 Mar31 Apr7 Apr|4 Apr22 Apr28 May5 May12 May19 .May27 3une2

Conrlo: i 24.4ab 27.5abc25.3a 19.9a 13.4a 14.8b 13.0ab i2.3cd 15.5bc 12.c1 13.2c

Methomyl 24.5ab 29.8a 20.gab18.6a 15.4a 15.8ab 12.gab 13.7cd 13.3c 13.3bc 14.bc1 0.9

Naled 23.9ab 26.3abc20,5b 18.6a 14.5a 16.4ab 15,1ab 12.3cd 13.4c 13.5bc 13.3c 1.0

Carbaryl 22.3ab 25.4bc 22.5ab24.1a 14.2a 13.lb 11.4b 11.5d 13.5c 11.9c 13.1c 1.5

Permethrln22.1ab 24.7c 20.7ab18.8a 16.0a 16.1ab 12.Sab13.3bcd16.5abc14.3b 15.7abc O_ _, 0.2

Abamectln 21.6b 29.0ab 19.7b 19.9a 14.3a 17.2ab 16.4a 15.7abc16.gab 16.4a 16.5ab 0.02

Abamectln 23.2ab 26.3abc2].4ab19.3a 15.9a 17.5ab 15.9a 13.8bcd17.7ab ]6.8a 16.6ab 0.02+ .1%oll

Abamectln 22.8ab 29.0ab 21.3ab20.0ab 16.la 17.4ab 16.5a 17.6a 16.0abe16.2a 16.9a 0.02In50gal/ac

FMC54800 23.7ab 28.8ab 20.6ab18.9a 15.7a 17.2ab 16.6a 15.gabc18.8a 17.4a 18.0a 0.05

FMC54800 27.la 28.4abc22.0ab19.3a 15.0a 19.5a 15.8a 16.0ab 19.9a 17.la 17.3a 0,l0 * All treatmentsappliedIni00gal/acunlessspecified. *MeansIncolumnsfollowedbythesameletterarenotsignificantdlyifferenatt P<0.05(DNMRT). Table6A. Effectsof pestlcldesonphotosynthesInisStrawberries.

Treatment* Meanphoto_vntrat;ehetIDerfivec leafsample** &lbAl/ac mar18M_r20AprI0 Apr17Act24May] Nla_8May16may22

Control 0.83a0.36a0.4lc 0.39c0.50bc0.33c0.48bc0.58ab0.62c

Methomyl *** 0,38a0.62bO./_7b0.c/_7c0.50bc0.35c0.59ab0.68bc 0.9

Naled 0.58b0.44a0.65b0.50bc0.68b0.45c0.4lc 0.53b 0.60c o, 1.0

Carbaryi *** 0.36a0.67b0.54b0.57bc0.40c0.40c0.67a 0.61c 1.5

Permethrin0.72ab0.42a0.65b0.69a0.93a0.65ab0.59ab0.61ab0.73ab 0.2

FMC548000.71ab0./_7a0.88a0.76a0.98a0.77a0.70a0.70a 0.79a ol.o *AiltreatmentsappliedIn100gal/Lniessac specified. **DataunitsareInmg CO 2 aSslmIlatedm-2 sec-lIMeansIncolumnsfollowedby thesame letterare not significantlydifferentat P(0.05(DNMRT). *** Data weFe notavailable. Table6B. Effectsof pesticideons stomatarlesistanceInStrawberries.

Treatment* M_anStomataresistancel perfivel_af___mp]e** &lbAl/ac Mar18Mar20Apr10ADF]7 Apr2qMayI May8 May16May22

Control 1.26b2.04a2.15a2.33a2o38a2.09al.gla 1.48ab2.03a

Methomyl *** 2.05a1,73b2.04ab2.35a1.93ab2.05a1.34bc1.88ab 0.9

Naled 1.78ab1,95a1.29cd2.06ab1.91b1.73b2.02a1.61a1,88ab 1.0

"4 Carbaryl *** 1,86a1.47bc1.93bc1.9lb 1.80b1.84a1.26c1.85abc 1.5

Permethrln1.48ab1.87a1.41bcd1.71o1:!.47c1.47c1.39b1.28c1.70bc 0.2

FMC54800 1.89a1.89a1.1Od 1.57d1.38c1.32c1.44b1.30bc1.66c o.lo * Alltreatmenappts liedIn100gal/aunc lessspecified. **Dataunitsaer InSeccra-1;MeansIncolumnsfollowedbythesameletterare notsignificandiffertly entatP<0.05(DNMRT). *** Datawerenotavailable. Table 7. Ovicidal efficacy of selected pesticides against Heliothis zea.

Treatment _n_ lb ai/acre Percent Mortality*

Ambush2EC 0"02 100a

Brigade10WP (1.10 100a

Lannate 90 WSP Q.90 100a

Sevin 80S 1.50 78b

Dibrom8E 1.00 72b

Cgntr¢ 13_ * Means followed by the same letter are not significantly different (LSD, P=0.05)

68 General Summary

Pro iect Title: Heliothi5 detection and control in strawberries

John T. Trumble, Project Leader Department of Entomology University of California, Riverside

Cooperators:

V. Voth W. Wiesenbom T. Perring Department of Pomoiogy Dept. of Entomology Dept. of Entomology Univ. Calif. Davis Univ. Calif. Riverside Unlv. Calif. Riverside

I. Detection and sampling studies.

Pheromone traps ('Texas' type) were placed in commercial and experimental strawberry fields in Orange County, California. The traps were checked weekly for adult Heliothis zee (Boddie) from 3anuary 1984 through June 1984. On each date the traps were monitored, we counted the number of H. zee eggs on ten plants adjacent to every trap (approximately 100 plants per week). Tomato fruitworm counts in traps were high, but egg counts were low. Additional studies using caged moths are planned for the spring of J987 to determine; 1) where on the plants the eggs are deposited and, 2) how long is the period between oviposition and penetration of the fruit.

From 3anuary 1986 through June of 1986 pheromone traps were monitored twice a week. Counts of eggs were made In adjacent corn fields to determine how the attractiveness of corn varied with growth stage. The availability and planting dates for nearby corn fields were provided by the IrvIne Company. Along with the first year's data, the trap catches were matched to major weather patterns to determine if pheromone traps could be used to predict outbreaks in strawberries.

The results of the pheromone trapping study were similar to those presented in the previous annual report. The first flight of adult I-4.zee were detected at low levels early in 1986, Increased through March and peaked at 60+ moths per trap in April. The flight then declined rapidly, demonstrating a strong periodicity which clearly defines a new generation. By early May, the next series of flights had begun. Although this flight also reached approximately 60 moths per trap, the majority of adult ._.H. Z_O were migrating to the neighboring corn fields which were increasing in attractiveness. Although the fifth flight in $une appeared to be the smallest, there were many H. zee present in the area, but the vast majority of these insects were congregating in the corn. Thus, the dynamics of intercrop movements plays an important role In determining if H. zee infestations will occur in strawberries. This aspect of our research will be studied again next year, to determine if this effect occurs regularly.

69 The pheromone trapping data have been related to major weather patterns. When combined with weather data on wind patterns and temperatures at heights favored by _H. zee, the following conclusions were made: 1) the adult moths were migrating on winds occurring at 850 millibars (mb) pressure, 2) moths aggregated at 850 mb when temperature inversions were present, and 3) wind direction and temperature were favorable for migration when a) Santa Ana winds began to decay, b) an onshore flow caused a weather pattern known as the Catalina Eddy to develop, or c) storms off the coast of Mexico generate stong winds from the south. A detailed analysis of weather patterns responsible for migratory movements will be presented in the final report for this project in t987.

The biology of _H. z_ on strawberries is currently under Investigation. A laboratory colony has been established at U.C. Riverside, and the numbers of insects are being increased. We anticipate continuing and completing the detailed biology studies during 1987.

II. Chemical Trials.

The primary purpose of this research was to generate information re. cessary for registration of new compounds for controlling Heliothis z_. In this study, an IPM approach was used to provide data on the impact of pesticides on the entire system, rather than just the target species. Groups responsible for registration have given strong consideration to registering new compounds when data demonstrates that currentlyregisteredpesticideswill:l)cause outbreaksof a non-target pest which requireuse of additionalpesticides,2)damage plantproductivitythrough reductions in photosynthesisor, 3) be unsuitablefor use in a resistancemanagement program. The experiments reported here were designedto determine the impact of both registeredand unregisteredcompounds with potentialfor H_liothiszee controlon populationsof two-spotted spidermttes.

Experimental desion - The test consistedof ten treatments includinga control. Each treatment was replicatedfour times in a randomized complete block design. Individualreplicateswere two-row beds which were 30 feet long. /MI pesticides were appliedgq alternateweeks from March 5 through May 28 (totalof seven applications).Actual dates of applicationswere: March 5 and 19, April 2, 16 and 30, May 14 and 28.

Art;hroood control: Brigade and Abamectin treatments provided the best control of spidermites (two spotted spidermite, Tetranvchus urticae). The Abamectin treatments incorporating 0.1% oil or using only 50 gallons of carrier per acre were generally better than Abamectin at 100 gal/acre. Methomyl, naled and carbaryl applications generated spidermite populations which were equal to or greater than those in the control plots. Permethrin offered some population reduction initially, but provided ltttle control after March 24. In spite of high densities of aphids at the beginning of the trial,all pesticides significantly and rapidly reduced populations. The primary species was Ch8etosiDhon f_gsefolH (Cockerell), the strawberry aphid, but Mvzus Derslcae (Sulzer) and Aphis gOSSVDii Glover were also present. The control plots tended to have more beneficial insects than any of the pesticide treatments, but

70 numbers of beneficialswere iow throughout the trial,and statisticalseperation between chemical treatments was not possible.

Yield and phytotoxicitveffectswere dearly associated.Brigade treatedplotshad the highestphotosyntheticratesand lowest stomata1 resistance(ie.resistanceto air movement into leaf),followed closelyby permethrin-treated relicates.All other treatments resultedinplotswith fewer fruit,lower harvestweights,and smaller fruit over the course of the season. This was probably due, in part, to the reductionsin photosynthesis and increases in stomatai conductance caused by either a sub-visual phytotoxic effect or the cummuiative impact of spidermite feeding. Phytotoxicity was also visually evident: burning of both leaves and fruit were recorded in the haled-treated plots. Note: naled is not recommended by the manufacturer for use at temperatures above 80_F. No phytotoxicity was observed for any of the other insecticides tested.

Laboratory Trial_ For Ov]cida] Efficacy: Insecticides were tested for ovicidaI activity against corn earworm eggs oviposited on excised strawberry leaves. Eighteen strawberry leaves with petioles in water were placed for 12 hours in a cage containing 30 mate and 30 female corn earworm adults. Randomly selected leaves were dipped in 400 mi of insecticide30 hours followingthe oviposltionperiod. Each leaf was an experimental unit; there were three replications,insecticideconcentrationswere based on 100 gal/acre. After the insecticidedried,i5 fertile(ringed)eggs from each leaf were isolatedby placing cut pieces of fresh leafeach with one egg on moist cellucottonin uncovered one oz plasiccups. Eggs were kept at 27+ l:C and evaluated forhatching96 hoursafteroviposition.

In managing corn earworm populationson strawberries,inflictingmortality during the egg stage w111 be a valuable control strategy. In these tests,the pyrethroidsappear to be the most useful in that they provided 100% suppression. Although L_annateprovided complete controlas well,the usefullnessof thischemical would be reduced by limitations placed on growers by processors. The other compounds in thistest,which alsoare registeredfor H. zea on strawberries,provided significantlylesscontrol.