POTENTIAL IMPACT OF COLEOMEGILLA-MACULATA PREDATION ON ADAPTATION OF LEPTINOTARSA-DECEMLINEATA TO BT-TRANSGENIC POTATOES

The relationship between Leptinotarsa decemlineata Say egg density and Coleomegilla maculata DeGeer predatory behavior was investigated at d ifferent spatial scales (plant-to-plant and plot-to-plot). Both adult C. maculata location and daily egg consumption rates were monitored ov er time in greenhouse and field tests. Despite aggregation in areas of highest prey density by C. maculata, egg consumption was inversely re lated to egg mass density at the smallest and the largest spatial scal es tested. The experimental data on predation rates in high and low de nsity field treatments were included in a mathematical model to simula te impact of natural enemies on the rate of L. decemlineata adaptation to Bt-toxin-expressing transgenic potato plants when Bt-expressing pl ants are mixed at the plot-to-plot level with normal potato plants. Re sults showed that C. maculata predatory behavior could decrease the ra te at which L, decemlineata adapted to Bk-toxins if plot-to-plot mixed -plantings were used.