Date: 3/29/99

Time: 8:00

Section: Student

Type: Poster

Number: D51

Impact of trangenic Bt sweet corn on beneficial insects: Evaluation of visual and sticky card techniques

*S.J. Wold, E.C. Burkness and W.D. Hutchison, Department of Entomology, University of Minnesota, St. Paul, MN 55108
Contact e-mail: wold0062@tc.umn.edu

Field and sweet corn Bt transgenic hybrids are effective options for controlling a major corn pest, the European corn borer, Ostrinia nubilalis (Hübner). A major concern with widespread use of transgenic crops is what effect the toxin-producing plant will have upon beneficial insect community structure. Field studies were conducted to determine if differences in beneficial insect populations occur between Bt sweet corn hybrids and their non-Bt isolines. Insect counts were obtained via two sampling techniques, visual and sticky card, at the whorl and silk stages. Yellow sticky cards were placed in the plant canopy and changed weekly. When cards were changed, beneficial species were visually identified and counted on three consecutive plants. Nine predatory species (Coleomegilla maculata, Adalia bipunctata, Hippodamia convergens, Hippodamia tredecimpunctata, Cocinella septempunctata, Harmonia axyridis, Chrysoperla plorabunda, Orius tristicolor, and Nabis spp.) were observed using both methods, and one parasitic species (Macrocentrus grandii) was observed only using the sticky cards. Analysis of variance tests indicated no significant differences in beneficial insect populations between Bt and non-Bt sweet corn, regardless of sampling technique. The method of sampling affected our estimate of the proportion of each species in the beneficial community.

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