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(24-06) Effects of transgenic field corn expressing two lepidopteran-specific insecticidal proteins on the invertebrate community . Dively, Galen*,1, Patton, Terrence1, Miller, Amy1, Nelson, Jessica1, Embrey, Michael1, 1 4112 Plant Sciences Bldg., College Park, Maryland ABSTRACT- A large-scale field study was conducted in Maryland in 2000-01 to determine the possible effects of transgenic field corn expressing two Bt-derived lepidopteran-specific insecticidal proteins, VIP3A and Cry1Ab, on the nontarget invertebrate community. The experimental design compared the transgenic hybrid to a non-transgenic, isogenic hybrid both with and without a foliar insecticide treatment for lepidopteran control. Three one-acre (0.4-hectare) randomized plots were evaluated for each treatment. The abundance and diversity of invertebrates representing both foliage-dwelling and soil surface fauna were monitored by visual inspections of plants, pitfall traps, sticky cards, and ear/litter extractions throughout the growing season and post-harvest. A total inventory of 201,548 organisms representing 78 families in the corn system was enumerated. In terms of diversity and abundance, approximately 52% of the invertebrates were saprophytes, 42% were herbivorous insects feeding on various parts of the corn plant, 5% were foliage- and ground-dwelling predators, and only 1% of the invertebrates were parasitic. Aside from the anticipated effects on lepidopteran target pest species, the transgenic hybrid had no significant negative effects on the invertebrate communities enumerated by the various sampling methods. Results lend strong support to the findings of other published reports that there are no unexpected tritrophic effects from transgenic lepidopteran-resistant corn on nontarget organisms. Some changes in certain taxa did occur but were indirectly linked to plant-mediated factors and the absence of feeding injury by target pest species. As expected, the communities of nontarget invertebrates in the insecticide sprayed plots displayed statistically significant changes in species abundance, diversity, and trophic interactions. Whether these changes will carry over to the following season remains unclear. However, the observation that the post-harvest litter communities of the three hybrid treatments were essentially the same lends support to the belief that disturbances associated with the foliar insecticide may be short-lived. Key words: transgenic crop, nontarget effects, Bt corn, multivariate analysis |
