Location: Southern Insect Management Research2009 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.
3. Progress Report
Objective 1-To study development of non-selected populations of bollworm (BW) and tobacco budworm (TBW) in crop hosts (soybean, corn and cotton), insect sampling in cotton, soybean(two maturity groups and two planting dates), and corn were conducted. Cotton produced budworm and bollworm. Corn produced bollworm only. In addition, soybean produced large numbers of bollworm larvae and very low number of tobacco budworm. Objective 2- To determine the potential of remote sensing techniques for detection and quantification of both wild and crop hosts of BW and TBW: Field crops and non-crop areas of vegetation on the Delta Branch Experiment Station, Stoneville, and at then off-station locations (main sites with variable number of sub-sites) were classified from early spring fall of 2006 by ratings of habitat type and quality for both bollworm and tobacco budworm. Discrete aerially acquired multispectral (red, green, NIR) images (Duncan 2100 digital video-camera) of each site off-station (forest and non-forest vegetation) and at on-station sites containing crops (corn, cotton, soybean, rice) were acquired at intervals as weather permitted) from early spring into the fall of 2006. In addition, multispectral (red, green, NIR) imagery was aerially acquired twice during the summer of 2004 over a large area (23 kilometers width) reaching from near Arcola, MS, to near Perthshier, MS, (104-kilometer width) with an ADS 40 video camera. Wild host populations at 12 sites have been assessed (spring through fall) for host suitability. A model is being developed to automatically grade the suitability for a site based on wild host constituents’ suitability for reproduction of BW and TBW for a given temporal position in the growing season. Imagery is being analyzed using spectral, structural features, and temporal setting to delineate wild host habitat. Objective 3- To study the economic impact of regulated transgenic Bt resistance management plans in cotton: An economic analysis of the impact of transgenic Bt cotton used three data resources, (1) USDA, NASS data for years 1996-2003, (2) state and country level on-farm data for years 1997-2009, and (3) economic threshold studies of Heliothinine species larval infestation on cotton in Mississippi. Results of analyzing four years of these data show that Bt cotton was slightly more profitable each year than conventional cotton with insecticide application. Insect control with insecticide applications to no-Bt cotton considerably reduced profit. Analyses of the net return for transgenic Bt cotton crops with 0, 1, 5, 10, 20, and 26 percent non-Bt cotton (refuges) showed consistently higher returns with each lower proportion of the crop planted in a non-Bt cotton variety. The returns were less when the non-Bt portion of the crop was sprayed. This project was monitored by face to face meetings at Stoneville and professional meetings.