1a.Objectives (from AD-416)
Investigate the length of persistence of the new soft insecticides in pistachios that target navel orangeworm (Amyelois transitella)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. Documents Trust Agreement with the California Pistachio Research Board. Log 38382.
This research supports objective 2 of the in-house project, by providing data necessary to improve insecticide application efficiency and reduce navel orangeworm infestation during the growing season, which in turn will reduce the need to fumigate pistachios. Studies conducted in Madera County evaluated the extent of application coverage at two ranches, using a combination of spray cards and navel orangeworm eggs as targets. The variables evaluated were spray rig type and application speed. Vertical distribution up to 20 feet was evaluated and the amount of droplets deposited at the greater heights decreased with application speed. Currently, the recommended application speed is 2 mph and these studies demonstrated that a substantial reduction in spray coverage occurred at speeds above this limit. Egg papers were paired with spray cards in order to determine a threshold level for application efficacy, but this experiment failed because of high variability. Nonetheless, this study quantified the relationship between droplet deposition and height, as well as the use of egg masses as targets. These studies will be continued with an emphasis on within row variability as well as application speed.