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Title: Effects of intra- and interpatch host density on egg parasitism by three species of Trichogramma

Author
item GRIESHOP, MATTHEW - KANSAS STATE UNIVERSITY
item Flinn, Paul
item NECHOLS, JAMES - KANSAS STATE UNIVERSITY

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2009
Publication Date: 1/15/2010
Citation: Grieshop, M.J., Flinn, P.W., Nechols, J.R. 2010. Effects of intra- and interpatch host density on egg parasitism by three species of Trichogramma. Journal of Insect Science. 10(99):1-14. doi: http://dx.doi.org/10.1673/031.010.9901.

Interpretive Summary: The Indianmeal moth is a serious pest of raw and finished stored products and attacks both packaged and bulk commodities as well as spillage. Three species of Trichogramma wasp parasitoids were tested to find the best one for biological control of the Indianmeal moth. We studied the effects of different intra- and interpatch Indianmeal moth egg densities on the host-foraging success of three different Trichogramma species. All three species parasitized the most eggs when they were arranged in a six by six patch array of four eggs per patch, and the least in the three by three patch grid of single eggs. Trichogramma deion parasitized significantly more eggs than T. pretiosum on the three by three grid of four-egg patches. Trichogramma deion may be the best candidate for augmentative biological control because it parasitized more eggs than the other two species in all four treatments. Trichogramma could provide a new tool for the retail organic food industry to manage insect pests. Harmless and practically invisible, Trichogramma wasps are an environmentally-friendly way to keep food pests in check.

Technical Abstract: Host-foraging responses to different intra- and interpatch densities were used to assess Trichogramma deion, T. ostriniae, and T. pretiosum as potential biological control agents for the Indianmeal moth (Plodia interpunctella). Single naïve females were allowed 6 h to forage in Plexiglas arenas with four different spatial arrangements of host eggs. No significant differences were found among species in the number of patches parasitized. All three species parasitized the most eggs when they were arranged in a six by six patch array of four eggs per patch, and the least in the three by three patch grid of single eggs. Trichogramma deion parasitized significantly more eggs than T. pretiosum on the three by three grid of four-egg patches. Trichogramma ostriniae parasitized significantly more patches when intrapatch density was greater, regardless of interpatch density. In contrast, T. deion only parasitized more patches at the greater intrapatch density when the interpatch density was low. Patch density had no effect on T. pretiosum. The spatial pattern of parasitism was more aggregated for T. deion and T. ostriniae in the six by six grid with four-egg patches compared to the six by six grid of single-egg patches. Therefore, intrapatch density was more important than interpatch density for T. ostriniae, and potentially for T. deion, but not T. pretiosum. Trichogramma deion may be the best candidate for augmentative biological control because it parasitized either slightly or significantly more eggs than the other two species in all four treatments. Furthermore, the pattern of parasitism by T. deion in the six by six grid of four-egg patches was the most aggregated among the three species, suggesting a more thorough searching pattern. In contrast, T. pretiosum had the least aggregated pattern of parasitism and may therefore have used a more random foraging pattern.