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Choosing the Best Refuge Hybrids for Planting with Corn Rootworm Resistant Bt Corn 2003

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Project Leaders: Margaret Smith, Department of Plant Breeding, Cornell University, and Laraine Ericson, Keith Payne, Department of Plant Breeding, Cornell University


John Losey, Department of Entomology, Cornell University

Leslie Allee, Department of Entomology, Cornell University

Type of Grant: Pest resistant crops.

Project Location(s): Throughout the Northeast.


Corn hybrids that have been genetically engineered with the Bt gene for resistance to corn rootworm offer growers in New York an interesting option for control of this pest. These hybrids would eliminate the need for soil-applied insecticides in many corn fields, but also require planting 20% of the area of the field with a non-genetically engineered variety (called a “refuge”) to ensure that Bt-susceptible rootworms continue to predominate in the rootworm population. Finding corn hybrids that are well adapted for refuge plantings will reduce the need for insecticide use in refuges, increase profitability from refuge plantings, and make it more likely that farmers will comply with the refuge requirement. Ideal refuge hybrids would suffer relatively little from corn rootworm damage (either because larvae do not damage them much or because they can regrow roots well and thus recover from the damage) and yet produce many adult rootworms to ensure that the rootworm population remains mostly susceptible to Bt. Our research was designed to identify such ideal refuge hybrids. Nine corn hybrids that are widely sold in New York were grown in plots that were infested with corn rootworm eggs and in plots that were not infested. Ratings of root damage and root regrowth after damage were made, and cages were installed in each plot to collect and count how many adult rootworms emerged. Based on just this initial year’s data, one hybrid appeared to be especially promising as a refuge hybrid, because it had excellent root regrowth and large numbers of adults emerged. It will take several more years of collecting data to confirm this result, and we will need to collect yield data (which is essential to evaluating damage to hybrids from rootworms, but could not be collected in 2003 because circumstances forced a very late planting date). In future years, we will be collecting data not only on rootworm damage, root regrowth, and adult emergence, but also on hybrid maturity, standability, and yield. This will provide a data set that will allow us to identify highly productive hybrids that serve as excellent refuge hybrids, thus providing growers with options to reduce or eliminate pesticide use in refuges, obtain more yield from them, and promote the effectiveness of genetically engineered Bt rootworm resistant corn in the future.

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