Aflatoxin Control During Plant Growth and Harvest of Corn

Extensive aflatoxin occurrence in corn both before and after harvest has prompted investigation to identify conditions contributing to crop infection by toxin-producing fungi. This presentation will attempt to summarize the preliminary observations of fungal-corn associations in the field in response to concern about this type of aflatoxin contamination. In the fall of 1972, a study of field corn in southeast Missouri and east central Illinois was initiated to examine the occurrence of the bright greenishyellow (BGY) fluorescence associated with Aspergillus flavus Link ex Fr. development and aflatoxin in white and yellow corn from about 70 fields (Lillehoj et al., 1975a) . Of 5,000 test ears, approximately 5 % exhibited fluorescence and 2.5 % contained aflatoxin B1 at levels exceeding 20 ppb (Table 1) . Field-to-field variation in aflatoxin incidence was significant; ears containing toxin-contaminated seed were found in 60 % of the fields. Distinct differences in toxin occurrence were observed between the five test regions of Missouri and the single test region of Illinois. Some aflatoxin-contaminated ears were obtained from each test region in Missouri but none were found in Illinois samples. Of the agronomic and environmental conditions examined, the only factor that correlated significantly with absence of toxin in Illinois corn was reduced corn earworm (Heliothis zea Boddie) damage; 21 % of the Missouri ears exhibited earworm activity vs. only 5 % damage in Illinois samples. Microbiological tests showed that kernels from insect-damaged ears contained a higher incidence of A. flavus than seed from insect-free ears (Fennell, Lillehoj, and Kwolek, 1975). Of 195 insects collected from test ears, A. flavus was found in 15 % of the specimens after culture on a nutrient medium.