Augmentative releases of parasitoid wasps in stored wheat reduces insect fragments in flour

Field studies were conducted to assess the effectiveness of the parasitoid wasp, Theocolax elegans, for reducing insect fragments in flour by suppress ing populations of Rhyzopertha dominica in six bins, each containing 27 ton nes of wheat. Beetles were released into all the six bins at monthly interv als for 3 months. Parasitoid wasps were released into three of the bins, 21 days after the first beetle release. Wheat samples from the bins were mill ed to determine the effects of parasitoid releases on insect fragment count s in flour. In the first year of the study, after 198 days of storage, inse ct fragment counts were 9.4 and 31 per 50 g flour in the treatment and cont rol bins. However, because of high variability, the means were not signific antly different. New grain was used in the second year of the study, and hi gher numbers of beetles were released. After 131 days of storage, fragment counts averaged 56 and 487/50 g in the treatment and control bins, a reduct ion in the former of 89%. In the second year of the study, insect myosin in the treatment and control bins averaged 0.27 and 3.23 ng/well, a percentag e reduction in the treated bin of 92%. The number of insect damaged kernels (IDK) was significantly lower in the treatment than in the control bins in both years of the study. In the first year, IDK was 6 and 15 IDK/100 g whe at in the treatment and control bins respectively, a reduction in the forme r of 61%. In the second year, IDK was 12 and 148 IDK/100 g wheat, in the tr eatment and control bins respectively, a reduction of 92%. This study showe d that augmentative releases of parasitoid wasps into bins of stored wheat reduced damage to wheat kernels and the number of insect fragments in flour . Published by Elsevier Science Ltd.