Thursday, August 9, 2007 - 4:00 PM

COS 120-8: Non-target effects of Bacillus thuringiensis transgenic corn on soil microarthropod community

Yiwen Zhao1, Deborah Neher1, and Galen P. Dively2. (1) University of Vermont, (2) University of Maryland

  Bacillus thuringiensi (Bt) is a species of insect-specific bacteria that has been developed as a microbial insecticide and widely applied in modern agriculture. In this study, we focused on the non-target effects of a coleopteran-active Bt corn on the soil mircoarthropod community, therefore exploring the potential ecotoxicological risk of Bt to agricultural ecosystems.
In 2003, three corn hybrids (transgenic YieldGard® Rootworm, which expressed a Cry3Bb toxin targeted for the corn rootworm complex Diabrotica spp.; isogenic non-transgenic hybrid treated with a soil insecticide for rootworm control as a conventional pest management control; and isogenic hybrid without insecticide as a genetic control) were planted in a non-till field in Maryland. Soil samples were collected three times per year (pre-plant, mid-season, post-harvest), and the following year in May (pre-plant) as well. Each treatment was replicated three times and the whole experiment was repeated in 2004 on adjacent plot without prior history of transgenic crops.
  Mites and collembolans were extracted from soil by heptane flotation, then enumerated and identified by genera. Repeated measures analysis of variance was performed to identify differences among cultivar treatments; further, canonical correspondence analysis was employed to explore patterns among cultivars and taxa using soil moisture as a covariable. Compared with the genetic control, Bt corn did not have a significant negative effect on the microarthropod community. The tolerance of microarthropods to insecticide differed by genera. A principal response curve analysis confirmed that treatment differences were consistent among years but patterns of seasonal fluctuation differed between 2003 and 2004, with an inconsistent magnitude of difference in community composition. Based on the results, we conclude that coleopteran-active Bt corn is ecologically more sound than application of conventional insecticides for control of corn root worm.