Monday, December 10, 2007 - 9:29 AM

Effect of host plants on successful parasitism by Haeckeliania sperata (Hymenoptera: Trichogrammatidae) on Diaprepes abbreviatus (Coleoptera: Curculionidae) eggs

Daniel Carrillo,, Jorge E. Peņa,, and Rita E. Duncan, University of Florida, Tropical Research and Education Center, 18905 SW 280th street, Homestead, FL

Diaprepes abbreviatus is a highly polyphagous root weevil considered pest of many native plants, fruit crops and ornamental commodities. Haeckeliania sperata is a gregarious endoparasitoid that attacks D. abbreviatus eggs. We hypothesized that the reproductive success of Haeckeliania sperata is affected by the host plant of D. abbreviatus. Six host plants with varying degrees of pubescence were used to determine successful parasitism and the effect of leaf trichomes on the searching behavior of H. sperata. No-choice tests revealed that H. sperata was able to parasitize Diaprepes eggs laid on the six host plants; however, the plants that bare a high trichome density in their leaves had a lower percent of parasitism than the plants with smoother leaves (p<0.01). Experiments removing trichomes from a host plant revealed that the presence of some leaf trichomes had a negative effect on the overall searching efficiency of H. sperata. The presence of trichomes decreased the net displacement (p<0.01) and increased the total search time (p<0.01) of H. sperata females, which results in a lower searching speed. Multiple regression analysis was used to establish the relationship between percent of parasitism and leaf trichome density, leaf thickness, or the searching speed of H. sperata .Searching speed was the best predictor of percent of parasitism (p<0.01, R2=0.89), this parameter could be used to predict the suitability of host plants for the establishment of H. sperata. Our findings suggest that the reproductive success of H. sperata is dependent on the host plant of D. abbreviatus.

Species 1: Coleoptera Curculionidae Diaprepes abbreviatus (Diaprepes root weevil)
Species 2: Hymenoptera Trichogrammatidae Haeckeliania sperata