Corn Insects: Management Options for Maximizing Profits
By Don Cook, Ph.D.
Delta Research and Ext. Center
Mississippi State University
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Several insect pests can impact field corn production in Mississippi. A complex of soil insect pests, including southern corn rootworm, wireworms, seed corn maggot, and white grubs, can infest corn fields and are usually present in the field at planting. These infestations are generally sporadic, but large infestations can severely reduce yield if not managed. Stink bug infestations during the early vegetative growth stages can also reduce yield. Fall armyworm is a sporadic pest of corn and can infest non-Bt corn. The response of corn to defoliation during the vegetative growth stages varies among growth stages. Corn earworm commonly infests non-Bt field corn, but rarely reduces yield when corn is planted during the recommended planting window. Bt corn was introduced to manage stalk borers, including European corn borer and Southwestern corn borer. The first Bt field corns that expressed one protein had minimal to moderate activity against corn earworm. Newer Bt corns that express multiple proteins exhibited much greater activity against corn earworm. However, the activity of some of these against corn earworm has declined as corn earworm has developed resistance to some of the Bt proteins. The impact of this has been minimal in field corn, because corn earworm rarely reduced corn yield. However following infestations in corn, the next generation of corn earworm infests cotton and other crops. The same or very similar Bt proteins that are deployed in field corn are also deployed in cotton. This has resulted in less than optimal performance of Bt traits in cotton and supplemental foliar insecticide applications in cotton have been needed.