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United States Department of Agriculture

Agricultural Research Service

Title: Effects of Maize Weevils (Coleoptera: Curculionidae) on Production of Aflatoxin B1 by Aspergillus Flavus

Authors
item Beti, J - UNIVERSITY OF WISCONSIN
item Phillips, Thomas
item Smalley, E - UNIVERSITY OF WISCONSIN

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 21, 1995
Publication Date: N/A

Interpretive Summary: Insects and molds are a threat to the quality and safety of stored grains and other stored foods. Aflatoxin B1 is a naturally occurring poison produced by the fungus Aspergillus flavus that infests grain in storage. This article reports a series of experiments that demonstrate that infestations of the maize weevil, a pest of stored grain, greatly increase the levels of aflatoxin in stored corn. Experiments utilized samples of corn that were infested with either weevils, spores of the A. flavus fungus, or combinations of weevils and fungus, and aflatoxin levels were determined using the biochemical method of enzyme-linked immunosorbant assay (ELISA). When weevils were combined with fungus spores and added to corn there was increased kernal moisture content and a five-fold increase in aflatoxin levels over corn that had spores added to it with no weevils. When insect damage to corn was simulated with a metal probe and then funga spores were applied, aflatoxin levels were higher than when spores were added with no damage. Mechanical damage caused by weevils and the higher grain moisture content that results from insect infestations clearly causes an increase in aflatoxin levels. Proper management of insect pests could reduce any increase in aflatoxin occurring in stored grain thus help to assure the public health.

Technical Abstract: This study investigated the role of maize weevils, Sitophilus zeamais (Coleoptera:Curculionidae), in enhancing aflatoxin B1 content in stored corn. In laboratory experiments aflatoxin B1 was quantified with an indirect ELISA on corn following infestation with adult weevils that had each been topically treated with 100 spores of A. flavus. Corn kernels infested with A. flavus-contaminated weevils had significantly higher levels of aflatoxin B1 than A. flavus- inoculated corn without weevils. The presence of maize weevils resulted in increased kernel moisture content during incubation, and grain moisture was positively correlated with aflatoxin content across treatments receiving spores. Aflatoxin B1 levels were higher in corn treated with fungus-contaminated weevils compared to corn that was mechanically damaged and inoculated with spores, but mechanically damaged corn had more aflatoxin than undamaged corn treated with spores. Aflatoxin B1 content in corn increased with time of weevil exposure from 7 to 21 days, but decreased after 28 days of exposure. These findings indicate that maize weevils facilitate the growth of A. flavus and aflatoxin production in corn as a result of both mechanical damage and increased moisture content. Weevil activity can have a profound effect on postharvest aflatoxin production even though little initial inoculum is present.

Last Modified: 4/16/2014
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