Effects of azadirachtin-based insecticides on the egg parasitoid Trichogramma minutum (Hymenoptera: Trichogrammatidae)

Effects of neem formulations on the reproduction and survival of the egg parasitoid Trichogramma minutum Riley were examined to assess the compatibility of the two control strategies in integrated pest management programs. A laboratory bioassay was developed for this purpose, which could be used as a model ecotoxicological system. Eggs of the Mediterranean flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), which had been treated with an acetone solution containing an azadirachtin-based formulation, were presented to individual T. minutum females. These eggs were held until parasitoids completed development and emerged from the eggs. Survival of T. minutum females 1 day after treatment, number of Mediterranean flour moth eggs parasitized, proportion of parasitized eggs from which adults emerged, and sex ratios of emerging adult parasitoids were determined. Two formulations of neem-seed extracts containing azadirachtin and a purified azadirachtin standard were tested at an operational dose and at 10 times the operational dose. At 50 g azadirachtin/ha (operational dose), no significant effects were observed on survival of parasitoid females. At 500 g azadirachtin/ha, female survival after 1 day was significantly reduced by Azatin EC and Neem EC. No reduction was evident with the 100% azadirachtin treatment, suggesting that other components of the formulations were in part responsible for the toxicity to females. Likewise, at 500 g azadirachtin/ha, the number of eggs parasitized was greatly reduced by Azatin EC and slightly reduced by Neem EC but was not reduced by an azadirachtin standard. These reductions in egg parasitism were probably due to the observed effects on female survival. At 500 g azadirachtin/ha, parasitoid developmental success was reduced by all treatments including the azadirachtin standard. Neem EC and Azatin EC at the lower dose also had a small but significant effect on developmental success. Sex ratio of emerging adults was not affected. These results indicate that azadirachtin is compatible with T. minutum during egg parasitism at operational dosages.

Release of native Trichogramma minutum to control grape berry moth

We studied the effects of inundative releases of the egg parasitoid Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae) on economic injury by grape berry moth, Endopiza viteana (Clemens) (Lepidoptera: Tortricidae). Trichogramma minutum originally collected from natural host populations near North East, Pennsylvania, was mass produced in tobacco hornworm hosts and Mediterranean flour moth. We released T. minutum in border rows, where grape berry moth infestation is typically high, of experiment field station and commercial vineyards from 1996 to 1999. We recorded significant reductions in economic injury in plots where parasitoids were released. In vineyards with low to moderate grape berry moth abundance, four releases during the growing season were adequate in reducing damage at harvest to below 3%. In high-risk vineyards, T. minutum releases reduced damage to levels below 15%. The use of buckwheat as a cover crop to provide nectar in combination with parasitoid releases showed potential benefits in parasitoid activity. A biocarrier and Biosprayer™ were used in mechanized parasitoid-release operations, and no adverse effect on parasitoid emergence was recorded from parasitized eggs using this approach.