Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2007
Publication Date: N/A
Interpretive Summary: This research was conducted to determine whether a relationship exists between damage to corn plants caused by the fall armyworm and aflatoxin contamination in the corn ear. Fall armyworm damage to plants has been indicated as a cause of reduced yield, and aflatoxin contamination of the corn ear is associated with plant stress, so the stress induced by the fall armyworm feeding could cause increased aflatoxin contamination of the grain. Tests were conducted for two years each at locations in Mississippi and Georgia, where plants were artificially infested with fall armyworm larvae and artificially inoculated with Aspergillus flavus, the fungus that produces aflatoxin. While significant leaf feeding damage was observed in plants that had been artificially infested as compared with those that were not infested, no correlation was observed with aflatoxin accumulation. While this may indicate that plant stress during the vegetative growth stages does not translate into increased susceptibility to aflatoxin accumulation in the reproductive stages, aflatoxin accumulation is highly variable and is strongly affected by the environment and a potential relationship between leaf damage and aflatoxin accumulation may have been obscured by variability for aflatoxin accumulation within the treatments.
Technical Abstract: Aflatoxin is produced by Aspergillus flavus Link ex Fries and is one of the most potent toxins found in nature. Contamination of corn grain with aflatoxin causes significant losses to farmers each year and is a major impediment to corn production in the southern U.S. Infection of corn grain by A. flavus has been correlated with ear-feeding by insects and with abiotic stresses such as heat and drought. Little is known about the potential for an association between stress induced by insect damage to vegetative tissues and contamination of corn grain with aflatoxin. In a two year study in Georgia and Mississippi, corn hybrids with different levels of resistance to the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) and aflatoxin contamination were artificially inoculated with both pests and evaluated for feeding damage and toxin accumulation. The lowest levels of aflatoxin contamination were observed among the transgenic (Bt) and aflatoxin-resistant hybrids. Consistent differences in aflatoxin contamination levels between fall armyworm-infested and non-infested plots were not observed at either location. While fall armyworm damage to early-stage corn plants can produce significant yield losses under heavy infestations, such herbivory may not predispose the grain to aflatoxin contamination.