| I investigated the nutritional suitability of corn pollen for Coleomegilla maculata larvae in the laboratory, developed laboratory assays designed to detect fitness reductions in C. maculata fed insect-resistant corn pollen and prey that had consumed insect-resistant plants, and examined the population responses and feeding behaviors of C. maculata and Harmonia axyridis under field conditions. We found that corn pollen from different hybrids is nutritionally variable, and certain critical nutrients for C. maculata development were at sub-optimal levels in some of the pollens. Also, the feeding efficiency of pollen-reared larvae changed over the larval stage, which could have important implications for the design of feeding assays aimed at evaluating the toxicity of insecticidal pollens. In other research, I found that ingesting corn pollen that contains the insecticidal protein Cry3Bb1 (from event MON 863), and aphid and lepidopteran prey that had fed on various insect-resistant corn hybrids (a conventionally bred hybrid that expresses mir 1, and transgenic hybrids that expressed Cry1Ab or Cry3Bb1) did not influence the fitness of C. maculata in the laboratory. This observation is in spite of the reduced quality of prey fed some of the insect-resistant hybrids. Finally, we observed that coccinellids respond to anthesis by increasing oviposition rates. Also, the majority of the guts of C. maculata larvae and adults collected from the field during anthesis contained corn pollen. In contrast, the adults and larvae of H. axyridis were more predatory than pollinivorous during anthesis. In conclusion, all life stages of C. maculata are exposed to insecticidal corn pollen in transgenic field corn and the majority of larvae and adults feed on corn pollen in the field; laboratory assays can be used to evaluate the toxicity of insecticidal corn pollen to C. maculata, but understanding the feeding behavior and nutrition of corn pollen is critical to the development of these laboratory assays; and prey-mediated impacts of insect-resistant crops on natural enemies are an important ecological pathway that requires more research. |
