Monday, December 11, 2006 - 8:47 AM

Effects of trehalulose feeding on parasitoid longevity

Jesse A. Hardin,, Mark K. Asplen,, and David N. Byrne, University of Arizona, Department of Entomology, 410 Forbes Bldg, Tucson, AZ

Insects, particularly phloem-feeding Sternorrhyncha, have been known to produce sugars in their honeydew (excreta) that are not found in their host plant. Bemisia tabaci has been shown to produce an isomer of sucrose, trehalulose (1-O-α-D-glucopyranosyl-D-fructose). B. tabaci is the only whitefly known to produce trehalulose in large quantities (>15% of total honeydew constituents), although other insects have been shown to produce the sugar in small amounts. Insect-derived sugars have been shown to reduce the longevity of honeydew-feeding parasitoids compared to sugars typically found in plant nectar sources. We were interested in determining if trehalulose was comparable to sucrose as a nutrient source for whitefly aphelinid parasitoids, and if this honeydew sugar could have differential effects on the longevity of parasitoids with differing life histories. Parasitoids were provided diets of either sucrose or trehalulose in varying concentrations (from 3mM to 2M) or a DI water control. Survival analyses and proportional hazard models were applied to test for an effect of diet on longevity. Sucrose and trehalulose were not significantly different in affecting survival when compared at the same concentration. Certain specific diets were significantly different in pairwise combinations. There was a significant effect of species, diet type and the interaction of these two factors on the longevity of the different parasitoid species; however, within species there was no significant effect of carbohydrate diet on longevity.

Species 1: Hemiptera Aleyrodidae Bemisia tabaci (sweet potato whitefly)
Species 2: Hymenoptera Aphelinidae Eretmocerus eremicus
Species 3: Hymenoptera Aphelinidae Encarsia formosa

[ Recorded presentation ] Recorded presentation