Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2001
Publication Date: 6/1/2003
Citation: DOWD, P.F. BIOTIC AND ABIOTIC FACTORS LIMITING EFFICACY OF BT CORN IN INDIRECTLY REDUCING MYCOTOXIN LEVELS IN COMMERCIAL FIELDS. JOURNAL OF ECONOMIC ENTOMOLOGY. 2003. v. 94(5). p. 1067-1074. Interpretive Summary: The presence of ear mold toxins in corn causes hundreds of millions of dollars in losses each year and limits the acceptability of U.S. corn to importers. Corn genetically engineered to produce a protein from an insect pathogen (Bt corn) has previously been shown to have much lower levels of the mold toxin fumonisin than corresponding nonBt corn when the European corn borer was the major pest. The present study, which was performed in commercial fields, indicated the presence of other insects, the type of hybrid, and the year-to-year and location-to- location environment can have an effect on how well this indirect control of ear mold toxins works. However, the Bt hybrids that expressed the protein at high levels in the silks and kernels still tended to have lower levels of fumonisins than those hybrids that expressed no or low levels of the Bt protein in these tissues. This work further demonstrates the potential usefulness of Bt corn in reducing mold toxins in corn in the Midwest, a strategy that should reduce the presence of the carcinogenic fumonisins in corn consumed by animal and people. This improved quality may help U.S. corn be more acceptable to importers due to lower levels of mold toxins. Because potential health benefits also occur with use of this genetically modified corn, this information may also result in greater acceptance of genetically modified material in the U.S. and abroad.
Technical Abstract: Incidence of insect damage and association of insect damage with mycotoxigenic corn ear molds and mycotoxins was examined in commercial fields of Bt and nonBt hybrids of different backgrounds in Illinois in 1998 and 1999. Nearly 50% Helicoverpa zea (Boddie) infestation sometimes occurred in Bt hybrids that express high levels of the protein in silks and kernels. European corn borer (Ostrinia nubilalis Hubner) damage was often uncommon, including in nonBt ears. Levels of total fumonisins were generally less (15 to 1.8 fold) in Bt vs. nonBt hybrids at the same site. There were several instances where there were no significant differences in fumonisin levels between low/no kernel Bt hybrids and Bt hybrids that produced high levels of the protein in the kernel and silk tissue. However, significant correlations were often noted between numbers of insect damaged kernels and total fumonisin levels, especially in 1998, suggesting in these cases that reducing insect damage was still reducing fumonisin levels. There was variability between the correlation coefficient for numbers of insect damaged kernels and fumonisin levels at different sites for the same year, different hybrids at the same site, and the same hybrid for different years. Although reductions in fumonisins in Bt hybrids were more limited than reported in the past, planting the Bt hybrids still appears to be a useful method for indirectly reducing mycotoxins in corn ears.