Many adult parasitoids utilize nectar sources which has been shown to increase their longevity and fecundity. The needs of adult parasitoids has led to the general assumption that parasitoids will be more abundant and healthier in diversified fields since they are benefiting from available nectar sources. However, the extent parasitoids actually utilize sugars in diversified crop habitats is largely unknown. Also, preliminary studies suggest that parasitoids might disperse far from nectar resources to locate hosts and understanding the spatial scale of the parasitoid's response to nectar resources is critical. Using biochemical sugar analysis, we studied the feeding activity of parasitoids in habitats with and without local nectar sources at various spatial scales. Sugar feeding by Diadegma insulare and Cotesia glomerata and parasitism rates of diamondback moth Plutella xylostella and imported cabbageworm Pieris rapae, their respective hosts, were monitored in cabbage plots with/without buckwheat border strips at two spatial scales. In one site, eight 12 m x 20 m cabbage plots with or without buckwheat strips were situated 67 m apart. In the large scale site, eight similar cabbage plots with/without buckwheat were situated a half a mile apart to minimize movement of parasitoids between treatments. We hypothesized that 1) parasitoids from plots with buckwheat will have a higher incidence of sugar feeding, and 2) sugar feeding by parasitoids will correspond with higher parasitism of pests. We also investigated whether treatment effects differed at the two spatial scales.
Species 1: Hymenoptera Ichneumonidae Diadegma insulare
Species 2: Hymenoptera Braconidae Cotesia glomerata
Keywords: sugar feeding, habitat diversification
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