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):
Almonds will be sprayed by commercial cooperators and collected at intervals over a 30-60 day period. These almonds 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.
This Trust agreement was established to support objective 2.B of the parent project; reducing insect pest populations, 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 primary pest of almonds and pistachios in California. Insecticide spray coverage was evaluated by exposing treated nuts to navel orangeworm egg strips containing a known number of eggs. Control egg strips were placed on unsprayed nuts. Initially there were three groups of nuts, Control, 1.8 mph and 2.4 mph, collected one day after application. Within each treatment nuts were collected between 18-20 feet (High) and between 5-7 feet (Low). All nuts were cracked and examined 6 weeks after infestation and all life stages present were recorded and pooled to calculate survival. At Day 1 after insecticide exposure, there was no difference between the two speeds or at the two heights. Overall, insecticide exposure reduced survival by 96.99% compared to the pooled Control survival. At Day 14 after insecticide exposure, there was a difference in NOW survival between the two speeds. Survival was higher in the nuts sprayed at 2.4 mph. Within the nuts sprayed at 1.8 mph, there was no difference in navel orangeworm survival in nuts collected in the Low and High canopy. The population was reduced by 91.8% compared to the control survival. At 2. 4 mph, there was a large difference in survival between the High and Low Canopy nuts. Egg strips placed in High Canopy nuts were 3.03 X as likely to survive than in Low Canopy nuts. Population reduction was 90.67% in the Low Canopy nuts and 71.74% in the High Canopy nuts. Failure started at the top of the tree and the rate of failure increased at the higher application speed. Although the insecticide treatment provided substantial protection at 14 Days after exposure, its efficacy clearly decreased compared to the first day after application. Application speed played a critical role in the protection provided by the insecticide.