BT RISK ASSESSMENT FOR LEPIDOPTEROUS PESTS OF COTTON
Southern Insect Management Research Unit
2011 Annual Report
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.
Field trials demonstrated the potential of yield loss caused by bollworms in Bt cotton expressing two proteins active against caterpillar pests (Bollgard II®). Bt cotton receiving supplemental insecticide applications reduced larval numbers and subsequent fruit damage and, in turn, improved lint yields. An additional study confirmed the risk associated with Bt resistance development in heliothines. Bollworm populations from Bt and non-Bt crops were exposed in the subsequent generation to various Bt cotton technologies. Progeny from populations collected on Bt crops had increased survival in the presence of Bt cotton than those populations from non-Bt crops. In an effort to evaluate ways to delay Bt resistance development in heliothines, new cotton and corn lines expressing multiple Bt proteins were evaluated against bollworm. New Bt cotton lines reduced bollworm and fall armyworm larval densities, as well as fruit damage compared to conventional varieties. Multiple-toxin corn hybrids reduced larval densities and ear feeding caused by bollworm. In the event that cross-resistance is not an issue between these toxins and those found in commercial varieties, the risk of Bt resistance in heliothines should be reduced. ADODR used site visit, email and telephone conferences to monitor activities of the project.