Bt Corn: Less Insect Damage, Lower Mycotoxin Levels, Healthier Corn

Bt corn that has been genetically modified to prevent damage by European corn borers may also be less likely to harbor mycotoxins, toxins produced by fungi on corn ears, according to an Agricultural Research Service entomologist.

Mycotoxins like fumonisin, a potential cancer-causing agent often found at elevated levels in insect damaged kernels, are both a health issue and an export issue. European and Asian markets can refuse to import U.S. corn because of what they rate as unacceptable levels of mycotoxins.

Related ARS research on—

Bt corn

• Versus caterpillars (4/98)

Fumonisins

• And beneficial bacteria (1/00)
• And horse disease (2/99)

European corn borers

• Repelled by "Ugly Duckling" corn (4/00)
• Lured by aroma of the Gaura plant (2/99)
• Thwarted by fungi (11/97)

Scientists have suspected higher mycotoxin levels may follow increased insect damage, but ARS entomologist Patrick F. Dowd found fumonisin levels 30- to 40-fold lower in Bt corn than in non-Bt varieties in Illinois cornfields. Bt stands for the biopesticide Bacillus thuringiensis.

Environmental conditions and the specific Bt corn hybrid play roles in the actual amount of reduction seen, but corn varieties that expressed the Bt protein throughout the plant rather than in specific areas were the least likely to have significant fumonisin levels, according to Dowd, who is with ARS’ National Center for Agricultural Utilization Research in Peoria, Ill. ARS is the U.S. Department of Agriculture’s chief in-house research agency.

While Bt corn is modified mainly to resist European corn borers, Bt corn also showed lower levels of mycotoxins when corn earworms were present in fields, although not as significant a reduction as when European corn borers were the primary insect pest.

This may encourage the creation of corn varieties with more resistance to a variety of insects in order to provide more protection from mycotoxins.

Small plot studies by Iowa State University plant pathologist Gary Munkvold appear to confirm Dowd’s findings.

Scientific contact: Patrick Dowd, ARS National Center for Agricultural Utilization Research, Peoria, Ill., phone (309) 681-6242, fax (309) 681-6686, dowdpf@mail.ncaur.usda.gov.