IMPACT OF STORED GRAIN PESTS ON SEED DETERIORATION AND AFLATOXIN CONTAMINATION IN MAIZE

Sitophilus oryzae L. and Tribolium castaneum Herbst were the dominant species of six major insect pests recorded from maize grains. The incidence of Aspergillus flavus group fungi as well as the level of aflatoxins were comparatively higher in insect damaged maize samples than the undamaged ones. Losses in stored maize, influenced by the above two insects, were studied for 15 weeks with or without inoculation by a toxigenic strain of A. flavus. Insect numbers, moisture content, germinability, dust weight production, mycoflora, especially A. flavus infection, and aflatoxin levels were measured. The number of insect species increased rapidly after 5 weeks in uninoculated samples and the multiplication rate of S. oryzae was greater than that of T. castaneum. In the presence of inoculated A. flavus, the population of live insects decreased after 10 weeks. The rapid growth of insects resulted in increases in moisture content of grains, dust weight production, A. flavus infection, and aflatoxin accumulation, in contrast to decrease in germinability. Toxigenic strains of A.flavus were isolated from both of the insect species.