Bentley, Walter J.

Holtz, Brent

Martin, Lee

Ribeiro, Brian

Wiley, Chris

Undetermined

ScholarsArchive@OSU

Chemical ControlDeveloping Insecticide Treatment Guidelines for Obliquebanded Leafroller,Choristoneura rosaceana, in PistachioWalt Bentley, IPM Entomologist, UC KearneyAgricultural Center, ParlierBrent Holtz, Farm Advisor, UCCE Madera CountyLee Martin, Brian Ribeiro, Laboratory Assistants, UC Kearney Agricultural Center, ParlierChris Wiley, Ranch Manager, AgriWorld, MaderaSummaryThe two objectives of the 2000 studywere to develop informationon timing insecticides forcontrolling obliquebandedleafroller(OBLR) and predicting the need to treat them. A producing10-year-oldpistachio orchard in Maderawas the study site. Monitoring ofmothswas begun inlate April and the first moth catchwas recorded on May 8, using TrecelC traps baited with thewestern strain of the OBLR pheromone. The pheromone cap was changed monthly. DegreeDay (dd) was calculated from that date. Treatments ofphosmet (Imidan®) were made using theequivalent of3.5 lbs active ingredient per acre. Treatments were made with an Air-O-Fan aircarrier sprayer driven at 2 mph and delivering 100 gallons ofmixture per acre. These treatmentswere begun on 5/25 (400 dd), 6/2 (600 dd), 6/9 (800 dd, not treated due to rain), 6/16 (1000 dd),6/22 (1200 dd), and 6/28 (1400 dd). In addition to the timing trial, an efficacy trial was done onAugust 2 where either esfenvalerate (10 ounces ofAsana®XL), tebufenozide (16 ounces ofConfrim®), phosmet (5 lbs. of Imidan® 70WP), and spinosad (4 ounces and 6 ounces ofSuccess®) were applied. Evaluation of the timing trial was done July 24 (counting live larvaefound on 30 trees, each for a minute), and the efficacy trial on August 31 (counting live larvae ona single tree for a minute).The threshold trial was accomplished by sampling two orchards during July by counting thelarval feeding sites on leaves for a minute per tree. Ten nut clusters from the same tree were thencounted and examined for those aborted by OBLR feeding. The number of leaves damaged (perminute count) was then correlated to the number of damaged nuts found in ten clusters.ResultsThe timing trial resulted in the 1000 and 1200 dd timings giving equally the most effectivecontrol based on the one-minute larval counts made on July 24 (Figure 1.). The 1000 dd timingresulted in an average of 5 live larvae found per minute of search and the 1200 dd timing resultedin an average of4.5 larvae per minute of search. These two treatments were significantly(P<0.05, Fisher's Protected LSD) better than the untreated checks and the 400 dd timing. Theywere not significantlydifferent from the 600 dd (15.75 larvae per minute of search) and the1400-dd treatment (11.75 larvae per minute of search). The established untreated controlaveraged 35.5 larvaeper minuteof searchandwas theworst treatment. The established800-ddtiming (not treated because of rain) resulted in 21 larvaeper minute of search and this was thenext worst treatment. If timing Imidan to control OBLR, 1000 to 1200 dd after the first male ofthe season provided the most effective control.The insecticide efficacy trial resulted in all four materials providing equally effective control ofOBLR. The four-ounce rate of Success was as effective as the six-ounce rate.113Therewas a direct relationshipbetween the number of OBLRdamaged leaves countedperminute and the number of damagednuts. This study is still in the preliminaryphase, butindications are that well over 20 damaged leaves counted per minute in July are needed beforenut damage is found.Conclusions and Practical ApplicationThe use of Imidan in the timed trials resulted in effective control if timed between 600 to 1200dd after the firstmale is trappedin the spring. However, themost effectivetimingwas 1000 and1200 dd after treatment.Touse this technique of timingapplication trappingofmalemothsmust begin before the firstmales are trapped. This means placing the pheromone traps by mid April in the southern SanJoaquin Valley and by May 1 in the northern San Joaquin Valley.Whenregistered, the biological insecticides suchas spinosadand tebufenozide, appearto beequal to the standardorganophosphate and pyrethroid in controllingOBLR.Finally, preliminary results showa goodrelationship between leaf feeding andnut damage byOBLR. The number of leaves damaged, measured in July by visual count for one minute, can beused to measure nut loss. However, considerable leafdamage is required before economic lossis found. This implies a relatively high treatment threshold for OBLR in pistachio.Figure 1. Live obliquebanded leafroller found on July 25, after various timed insecticideapplications.400 dd 600 dd 1000dd 1200 dd 1400 dd Untreated Untreated1 2114

Developing Insecticide Treatment Guidelines for Obliquebanded Leafroller, Choristoneura rosaceana, in Pistachio

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Developing Insecticide Treatment Guidelines for Obliquebanded Leafroller, Choristoneura rosaceana, in Pistachio

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