INSECT DAMAGE AND AFLATOXIN CONTAMINATION IN PREHARVEST CORN: INFLUENCE OF GENOTYPE AND EAR WETTING1,2

Abstract

A corn, Zea mays L., hybrid with loose-husk characteristics developed for the Corn Belt and a hybrid with tight-husk characteristics developed for the South were evaluated in field plots for relative levels of corn earworm [Heliothis zea (Boddie)] feeding damage, visible Aspergillus flavus sporulation, and aflatoxin contamination in 1980 and 1981. Supplemental corn earworm eggs and A. flavus spores were applied to silks of all ears. Water treatments consisted of an untreated check and a water spray (simulated heavy morning dew) applied to developing ears either once or 3 times per week for 4 weeks. Water was applied to ears with a hand-held garden sprayer until runoff occurred. The southern-adapted hybrid with good husk cover sustained significantly less insect damage and aflatoxin contamination than the Corn Belt-adapted hybrid during both years. Significant differences between hybrids (5% level) in visible A. flavus sporulation were obtained only in 1981. Corn plots treated with 3 water sprays per week for 4 weeks tended to sustain more insect damage, visible A. flavus, and aflatoxin than plots sprayed with water once a week for 4 weeks, although significant differences at the 5% level were obtained for aflatoxin concentrations only in 1981. These data demonstrate significant levels of insect resistance and resistance to aflatoxin development between two corn genotypes. Also, heavy morning dews that frequently occur in the Southeast may be involved in the elevation of aflatoxin contamination in this area.