1998 ESA North Central Branch Meeting Abstract
65 WILL FARMERS USE SOIL INSECTICIDES IN THE NEXT CENTURY? J. J. Tollefson, Department of Entomology, Iowa State University, Ames, IA 50011-3140
Currently there is a great deal of excitement over transgenic corn that contains a gene from Bacillus thuringiensis. In some varieties the gene results in near immunity to all generations of European corn borer larvae. An even bigger market for insecticides than the European corn borer is the corn rootworm. In most fields where corn is planted after corn, an insecticide is applied to the soil at planting time to guard against rootworm larval injury. Because of the size of this market, seed producers are working hard to produce genetically modified varieties that are resistant to the rootworm. It is estimated that elite, transgenic, rootworm-resistant varieties of corn will be available early in the next century. Will the introduction of rootworm transgenic varieties eliminate the use of soil insecticides? At present it is required that a susceptible refuge be planted if an insect resistant transgenic variety is planted. If the refuge is large enough, an insecticide may be applied to help reduce the losses in the refuge planting. The favored approach for corn borers is to plant the refuge as large, contiguous blocks. This may not be the best choice with corn rootworms because it is likely that they will mate prior to moving away from where the emerged. A more effective approach might be to interplant the refuge throughout the resistant planting. A reasonable way of protecting the susceptible rows would be to apply an insecticide at planting. One or two rows of seed hoppers could be filled with susceptible seed and insecticide boxes mounted on those rows. The use of band-applied, soil insecticides would reduce the required size of the refuge because, while protecting the plant from lodging, they allow nearly half the larvae to survive, producing adults to interbreed with those that survive the transgenic hosts.
This paper will be presented on Monday.
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