1a. Objectives (from AD-416)
Determine the associations of navel orangeworm (NOW) (flight, oviposition, wounding of nuts by larvae and adult moths) with aflatoxigenic fungi Aspergillus flavus and A. parasiticus. Also determine the ability of NOW to vector propagules of A. flavus/A. parasiticus, when nuts become susceptible to infestation by NOW, and compare the vectored fungi with those producing aflatoxins in nuts.
1b. Approach (from AD-416)
Larvae and pupae from nut mummies from the trees and the ground and NOW moths will be collected periodically from commercial pistachio and almond orchards and the insects plated on specific media to determine the levels of contamination. Strains of A. flavus/A. parasiticus isolated from NOW will be compared with those isolated from infected nuts. Pea size and crinkled pistachio (NOW-damaged and non-damaged, stained, and not stained) will be plated periodically to determine their infection by Aspergillus spp. To determine when nuts become susceptible to NOW, we will periodically bag pistachio clusters and almonds with NOW. All the isolates of S, L, and M strains of A. flavus and A. parasiticus will be identified based on previously published research. Documents SCA with Kearney Hort. Station.
3. Progress Report
This research contributes to Objective 1 of the in-house project. The goal of this project is to determine the relationship between navel orangeworm damage and aflatoxin contamination of pistachios in the San Joaquin Valley. One ARS entomologist and one plant pathologist from UC Davis, based in Parlier, CA are collaborating on this project. More than 50,000 navel orangeworm adult males were collected using female baited traps in Madera and Fresno counties and a subsample of these adults was plated in order to identify the species of Aspergillus on their bodies. The prevalence of aflatoxin-producing Aspergillus varied during the season, increasing in September coincident with harvest. Additional studies were undertaken to determine whether a competing, non-aflatoxin producing fungus, could be successfully established in pistachios. Cooperator activity was monitored by reports at a stakeholder meeting in August, presentations made to the Almond Board of California, telephone conversations and e-mail.