1a.Objectives (from AD-416)
The objective of this cooperative research project is to conduct risk assessment research for Lepidopterous pests of Bt-crops. This research should enhance Bt-resistance management strategies which are designed to delay the onset of resistance development in target insects.
1b.Approach (from AD-416)
This agreement will determine the effect of Bt crop production on the population genetics of bollworm, tobacco budworm, and fall armyworm. Specific issues will be:. 1)a better overall understanding of gene flow and population structure for the pests,. 2)Bt-resistance allelic frequency estimates over time,. 3)the impact of changing refuge strategies and dynamic agroecosystems on managing resistance to Bt, and,. 4)the impact of Bt-suppressed population densities on insecticide resistance, e.g. the recent pyrethroid resistance in bollworm. The cooperator will be actively involved in all phases of this research including the collection of test insects from across the U. S. Cotton Belt. Pyrethroid resistance assays will be conducted in cooperators laboratory. Insect tissue will then be sent to the USDA-ARS for use in genetic marker analysis and carbon isotope analysis. Other technologies (e.g. secondary plant chemical detection in insect tissue and oxygen and nitrogen isotope analysis) will be used as they become available to further understand the population ecology of the pests in relation to Bt resistance management.
Multiple experiments were conducted to address this project. An experimental transgenic Bt cotton line was evaluated for efficacy against multiple lepidopteran pests. The experimental cotton line exhibited efficacy similar to other commercially available Bt cottons. Resistance management plans for this cotton should follow the plans outlined for other Bt technologies. In other experiments, corn hybrids with multiple toxins for above ground lepidopteran insects have been evaluated. These hybrids express significantly better activity against Helicoverpa (H.) zea (corn earworm, bollworm) than single toxin Bt corn hybrids. This increased efficacy is likely to have a significant impact on the population dynamics and resistance management strategies for H. zea, an important insect pest of cotton. To date, no H. zea larvae have been observed completing development in these corn hybrids. Future experiments will focus on the long term impacts of these corn hybrids on the population dynamics of H. zea. The project was monitored through emails, telephone calls, and site visits.