Augmentation of the egg parasitoid Anaphes iole (Hymenoptera: Mymaridae) for Lygus hesperus (Heteroptera: Miridae) management in strawberries

The impact of repeated releases of Anaphes iole (Girault) on the development of Lygus hesperus Knight populations and fruit damage on commercial strawberry fields was evaluated. Following the release of 37,000 parasitoids per hectare, 50% of L. hesperus eggs were parastitized. Parasitism levels declined rapidly; after 96 h, parasitism levels had declined to an average of only 3.5% in these plots. A release rate of 12,300 parasitoids per hectare produced parasitism levels of 6.3 and 7.0% 4S and 96 h after release, respectively. The high release rate of the parasitoids resulted in a 43% reduction in the number of L. hesperus nymphs and a 22% reduction in the amount of fruit damage. The low release rate responded in a comparable fashion, with nymph and damage levels 19 and 14% lower than control plots, respectively. The effect of the parasitoid releases on the L. hesperus populations increased through time. On average, there was a proportionally greater reduction in nymph densities in the higher release rate plots during the latter half of the season. In all the plots, there was a significant relationship between the number of L. hesperus nymphs found in the plot and the amount of fruit damage. The significance of these results to management of L. hesperus in strawberries is discussed.