1a. Objectives (from AD-416):
Investigate the length of persistence of the new soft insecticides in pistachios that target navel orangeworm (Amyelois transitella), using bioassay and analytical chemistry,and assess spray coverage.
1b. Approach (from AD-416):
Pistachios will be sprayed by commercial cooperators and collected at intervals over a 30-60 day period. These pistachios will be challenged in the lab by infesting them with known numbers of eggs and assessing adult emergence. Samples will be taken from the hull and environment and analyzed to determine insecticide residue, which will be linked to the success of the bioassays. Additional experiments conducted in the field will assess insecticide coverage using sentinel eggs and spray cards.
3. Progress Report:
This trust agreement was established to support research Objective 2 B of the parent project, reducing insect pest populations to reduce the need for post harvest treatment as well as promoting the use of selective rather than broad spectrum insecticides to control navel orangeworm. The navel orangeworm is the primary lepidopteran pest of pistachios in California. It is currently controlled by insecticides but considerable questions remain concerning both the optimal insecticides to use as well as the proper timing of applications. An ARS scientist at Parlier evaluated the duration of control in Madera county provided by an aerial application of the pyrethroid insecticide bifenthrin, flown over approximately 3500 acres on July 15, 2012. Adult male populations were monitored using virgin female traps and this aerial application depressed male capture for 17-19 days. A follow-up aerial application made in mid September did not depress male capture. These data indicate that pyrethroid insecticides have a greater impact in the period mid August through early September and/or that it is difficult to bring a population of navel orangeworm under control once it has had the opportunity to drastically expand. Further experiments with other classes of insecticide are needed to determine the feasibility of depressing populations in mid to late September. Current research is focusing on both the adult activity and ovicidal activity of more selective insecticides, with the goal of phasing out or drastically reducing reliance on broad spectrum pyrethroid insecticides. This research has the potential to reduce the overreliance on pyrethroid insecticides and improve navel orangeworm control. Improved control will increase the quality of pistachios and boost their exports.