EFFECTS OF MAIZE WEEVILS (COLEOPTERA, CURCULIONIDAE) ON PRODUCTION OFAFLATOXIN B-1 BY ASPERGILLUS-FLAVUS IN STORED CORN

Insects play an important role as facilitators of the aflatoxin-produc ing fungus, Aspergillus flavus Link, in both preharvest and postharves t corn. The current study investigated the role of maize weevils, Sito philus zeamais Motschulsky in enhancing aflatoxin nl content in stored corn. In laboratory experiments, aflatoxin B-1 was quantified with al l indirect enzyme-linked immunosorbent assay (ELISA) on corn following artificial infestation with adult weevils that had each been topicall y treated with 100 spores of A. flavus. Corn kernels infested with A. flavus-contaminated weevils had significantly higher levels of aflatox in B-1 than A. flavus-inoculated corn without weevils. The presence of maize weevils resulted in increased kernel moisture content during in cubation, and grain moisture was positively correlated with aflatoxin content across treatments receiving spores. Aflatoxin B-1 levels were higher in corn treated with fungus-contaminated weevils compared with corn that Mras mechanically damaged and inoculated with spores, which in turn had more aflatoxin than undamaged corn treated with spores. Af latoxin B-1 content in corn increased with time of weevil exposure fro m 7 to 21 d, but decreased after 28 d of exposure. Aflatoxin levels in infested corn increased significantly with increased numbers of A. fl avus-contaminated weevils. Maize weevils carried spores both internall y and externally; however, substantial numbers of spores were intimate ly associated with the exoskeleton of adult weevils. These findings in dicate that maize weevils facilitate the growth of A. flavus and aflat oxin production in corn by increasing surface area susceptible to fung al infection and increasing moisture content as a result of weevil met abolic activity. Weevil activity can have a profound effect on posthar vest aflatoxin production even though little initial inoculum is prese nt.