The contribution of diet supplementation in braconid parasitoids longevity, egg load, and egg volume

Wheat stem sawfly (WSS), Cephus cinctus Norton (Hymenoptera: Cephidae), is a major pest of wheat, causing losses that exceed $350 million annually across the Northern Great Plains. Two parasitoids, Bracon cephi (Gahan) and Bracon lissogaster Muesebeck (Hymenoptera: Braconidae), are well known as biological control agents of WSS. The success of natural enemies is linked to access to supplemental food in the field. Therefore, to assess the benefits that nectar types might have on parasitoid biology, adult females were reared on carbohydrate-rich diets combined with amino acids or uncombined, with water and amino acids as a control. Females were observed daily to assess longevity. Results show that both species increased longevity when provided carbohydrate-rich food, especially when combined with amino acids. Knowing that the supplemental food source parasitoids are feeding on has potential to increase reproductive success, we are testing cowpea (Vigna unguiculata L. Walpers) as an extrafloral nectar (EFN) resource for parasitoids. Females were checked daily for longevity and egg size was measured on day 0, 5 and 10. Our results show that EFN increases parasitoids longevity and maintains constant egg load and volume, and thus would be a good source of parasitoid nutrition.In addition, EFN are an open resource easily accessed by these braconids. We hypothesize that not only the use of a cover crop such as cowpea, but also the use of other flowering strips adjacent to wheat fields may be beneficial, contributing to the conservation of natural resources while benefiting both B. cephi and B. lissogaster