ARS | Publication request: Aflatoxin in corn hybrids infested at different growth stages with southwestern corn borer (Lepidoptera: Crambidae)

Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 28, 2007
Publication Date: April 1, 2007
Citation: Williams, W.P., Windham, G.L., Buckley, P.M., Daves, C.A. 2007. Aflatoxin accumulation in corn hybrids infested at different growth stages with southwestern corn borer (Lepidoptera: Crambidae). Journal of Agricultural and Urban Entomology. 23:97-103.

Interpretive Summary: Contamination of corn grain with aflatoxin, which is produced by the fungus Aspergillus flavus, is a major impediment to profitable corn production in the southern United States. Aflatoxin is toxic to livestock, pets, and humans. It is also a human carcinogen. Sale of grain with levels of aflatoxin higher than 20 ppb is restricted from interstate commerce. This study was undertaken to investigate the relationship between southwestern corn borer damage and aflatoxin accumulation in corn. Corn hybrids were infested weekly from 5 to 12 weeks with southwestern corn borer larvae, and aflatoxin was measured at harvest. Conventionally bred commercial corn hybrids sustained the highest levels of contamination. Hybrids with resistance to southwestern corn borer damage exhibited lower levels of aflatoxin contamination. A hybrid selected for resistance to aflatoxin contamination per se had the lowest level of contamination. The results of this investigation indicate that southwestern corn borer damage increases the likelihood of aflatoxin contamination. Hybrids with both resistance to southwestern corn borer damage and aflatoxin contamination per se would be the most effective way to significantly reduce aflatoxin contamination.

Technical Abstract: Aflatoxin is a potent toxin produced by the fungus Aspergillus flavus. Contamination of corn, Zea mays L., with aflatoxin greatly reduces the value of corn grain and is a major impediment to profitable corn production in the South. Infestation of developing corn ears with southwestern corn borer, Diatraea grandiosella, increases the level of likelihood of aflatoxin contamination. In this investigation six corn hybrids with different levels of resistance to southwestern corn borer damage and aflatoxin contamination were evaluated for damage by southwestern corn borer and aflatoxin contamination after infestation with southwestern corn borer at 7 d intervals from 35 to 84 d after planting and inoculation with an A. flavus conidial suspension. Transgenic (Bt) hybrids exhibited excellent resistance to southwestern corn borer and less aflatoxin contamination than conventional versions of the same hybrids. A conventional hybrid with intermediate resistance to southwestern corn borer also exhibited relatively low levels of aflatoxin contamination. A conventional hybrid selected for resistance to aflatoxin contamination was heavily damaged by southwestern corn borer, but exhibited little aflatoxin contamination. Hybrids that have resistance to both southwestern corn borer and aflatoxin contamination appear to have the greatest potential for effectively reducing losses to aflatoxin in the South. Damage by southwestern corn borer to plants in both the vegetative and reproductive stages of growth can increase aflatoxin contamination in susceptible corn hybrids.