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.
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 duration of control provided by the insecticides Belt, Brigade, Delegate, Imidan, Intrepid, and Warrior in Madera and Tulare counties was evaluated. A novel assay method employing navel orangeworm eggs was developed to evaluate both spray coverage and confirm initial insecticide efficacy, using strips of paper containing eggs that were pinned to pistachio clusters. Clusters were randomly chosen to ensure that interior, exterior, low and high positions were equally represented. The eggs were removed 24 hours after exposure, transferred to artificial diet, and the surviving larvae counted three weeks after exposure. A total of 50,905 eggs were exposed to Brigade in 5 trials conducted in Madera County. Mortality ranged from 79.02% - 99.73% in these trials. In four trials Brigade was applied by tractor and in the fifth trial Brigade was applied by air (95.5% mortality). A total of 3,563 eggs were exposed to Warrior, 13,902 eggs was exposed to a mixture of Warrior and Intrepid (Warrior at 5 ounces per acre, Intrepid at 16 ounces per acre) and 12,256 eggs were exposed to Belt. Every trial utilized eggs pinned on nontreated clusters as a control. In general, all of the insecticides tested had excellent contact toxicity. There was variation between trials and coverage was unsatisfactory in the Brigade trial that produced 79% mortality. Variation within a trial was quantified in additional experiments conducted in Madera County. In this experiment egg targets were placed in 4 rows and mortality was assessed. In two rows, mortality was 99.02% and 98.38%, and in the remaining rows mortality was 94.46% and 94.96%, respectively. In order to maintain a population without increase, the mortality for the generation must be 98%.