|Burks, Charles - Chuck|
Submitted to: California Pistachio Commission Production Research Report
Publication Type: Trade Journal
Publication Acceptance Date: 2/16/2005
Publication Date: 2/26/2005
Citation: Burks, C.S., Higbee, B., Kents, D., Bentley, W., Kuenen, L.P. 2005. Navel orangeworm abundance and damage in pistachios. California Pistachio Commission Production Research Report.143-153. Interpretive Summary: The navel orangeworm Amyelois transitella (Lepidoptera: Pyralidae) is a key pest of almonds, pistachios, and figs in California. Damage from this pest is caused by the larvae, which feed directly on nuts or drying fruit. The sole component identified from the blend of compounds comprising the sex pheromone is not sufficient to attract males to a trap, and therefore data on seasonal abundance of this species in these crops has been lacking. We used virgin females as a pheromone source to confirm differences in seasonal abundance of navel orangeworm in almonds and pistachios on a large scale (640 acres) and used female-baited flight traps and oviposition traps to demonstrate that these differences in adjacent 20 acre block of pistachios and almonds or figs. We found that, for much of the season, navel orangeworm abundance was higher in pistachios than in almonds. Damage from navel orangeworm larvae was nonetheless lower in pistachios than in almonds. This is likely the cause of differences we observed between the effects of mating disruption and insecticide treatments on navel orangeworm damage in these two crops.
Technical Abstract: Data collected in 2004 from 640 acre plots confirm data from the previous growing season indicating that navel orangeworm (Amyelois transitella) abundance is greater in pistachios than in almonds, particularly prior to late July. Data collected in 2004 from 20 acres plots of pistachios adjacent to 20 acres plots of almonds or figs corroborate the large plot findings, although on this smaller scale differences in navel orangeworm abundance are more evident in egg counts from oviposition traps than in counts of males in pheromone-baited flight traps. Pistachios can tolerate high abundance of navel orangeworm adults (i.e., 25-100 males per pheromone trap per week) 2-4 weeks before harvest without sustaining damage of greater than 2%. This same abundance of navel orangeworm adults in Nonpareil almonds 2-4 weeks before harvest results in higher damage. We have found >25 navel orangeworm males per trap per week in all pistachios in Kern and Madera County that we have monitored with flight traps using females as a pheromone source, regardless of sanitation practices or insecticide applications. These observations suggest that, while almond producers can affect both navel orangeworm abundance and harvest date within a range that has practical impact on economic loss from this pest, in pistachios this is true only for harvest date and not for abundance.