Will EPA change CRW refuge requirements?
More Refuge Acres
Gray points to the importance of “integrating management practices such as rotating corn with other crops, rotating Bt traits from season to season, considering the use of a non-Bt hybrid along with a soil insecticide at planting, and not neglecting the use of a refuge if a Bt hybrid is planted.” On the issue of a refuge, Gray pushes some recommendations of other corn rootworm experts to the forefront.
In another publication, he quotes the authorities as saying the current refuge requirements are insufficient because the corn does not meet a high-dose standard and rootworms have rapidly developed resistance in the laboratory, greenhouse and field. Accordingly, we recommend increasing the minimum refuge for Bt corn targeting corn rootworms to 50% for plants producing one toxin active against these pests and to 20 percent for plants producing two toxins active against these pests. Increasing the minimum refuge percentage can help to delay pest resistance, encourage integrated pest management, and promote more sustainable crop production.”
Will the EPA step into the picture and either remove the hybrids with the Cry3Bbi protein from the market or push your acreage requirements up to 50 percent? Gray says the EPA response is “murky.” He said a scientific advisory panel had initially suggested a 50 percent refuge, but the EPA instead initiated a 20 percent requirement. Gray says a new technology to fight corn rootworms is at least as far away as the year 2020.
Although corn fields are being found with the Cry3Bbi protein that seemed to have lost its toxicity to rootworms in Iowa last year, entomologists are not ready to proclaim its worthlessness in Illinois. However, many fields that bear that gene as the only measure of protection have been found with pruned corn roots and many adults on growing corn stalks. Along with the research on potential loss of resistance come suggestions that refuges be enlarged to 50 percent, of a producer is planting corn that has only a single protein designed to fight corn rootworm.