St. Paul, Minn. (October 1, 1999)—The recent approval and commercial release of genetically modified, insect-resistant corn hybrids (Bt corn) represents the culmination of decades of research. This innovative technology has a distinct health benefit of discouraging the build up of mycotoxins in corn, potentially dangerous human and animal toxins produced by fungi that cause plant disease.
Mycotoxin build up is directly related to certain fungal plant diseases, which can be increased by insect damage in crops. Insect larvae chew on stalks and kernels, creating wounds where fungal spores can enter the plant. Once established, these fungi often produce mycotoxins. Some mycotoxins such as fumonisin, can be fatal to horses and pigs, and are probable human carcinogens. "Lower mycotoxin concentrations in Bt corn hybrids clearly represent a benefit to consumers," says Gary Munkvold, plant pathologist at Iowa State University and a member of The American Phytopathological Society. "Studies show Bt corn hybrids that control European corn borer damage to kernels usually have very little Fusarium ear rot, and consequently, lower fumonisin concentrations."
Bt corn hybrids control feeding by the European corn borer and to some extent closely related insects such as the corn earworm, common stalk borer, armyworm, and Southwestern corn borer. All of which cause mechanical damage to the corn which influences the development of several crop damaging diseases including ear rots, kernel rots and stalk rots.
Kernel rot caused by the fungus Aspergillus is also associated with insect damage to ears. Several species of this fungus produce the most notorious mycotoxins found in corn, the aflatoxins. "The economic impact of aflatoxins has been greater than that of other mycotoxins in corn because aflatoxins can be passed into milk if dairy cows consume contaminated grain," says Munkvold.
Bt corn hybrids can be an important tool in the integrated management of corn ear and stalk rots and a boon to the environment as well. "Using genetically modified hybrids to control insects and diseases offers an alternative that is much more effective, consistent, economic and environmentally sound than foliar insecticides. For example, non-Bt hybrid sweet corn can require 12 or more insecticide applications in a single season for the production of sweet corn for fresh market sales."
Controversy over production and use of genetically modified crop cultivars has focused a great deal of public attention on Bt corn. "Debate surrounding the use of genetically modified crops should be based on risk/benefit assessment, including environmental impacts, livestock impacts, and potential human health threats," says Munkvold. "Consumers and regulatory agencies should consider the food safety and environmental implications of Bt corn when making decisions about its use."
For more information about Bt corn, read the APS feature story at www.apsnet.org/publications/apsnetfeatures/Pages/InsectResistantCorn.aspx. The American Phytopathological Society (APS) is a professional scientific organization dedicated to the study and control of plant disease with 5,000 members worldwide. If you would like to receive copies of all news releases issued by APS, please send an e-mail to us here.
