INTERACTIONS BETWEEN MAIZE WEEVIL (COLEOPTERA: CURCULIONIDAE) INFESTATIONS AND INFECTION BY ASPERGILLUS FLAVUS AND OTHER FUNGI IN STORED CORN

Abstract

Thirty adult maize weevils, Sitophilus zeamais Motschulsky, were placed in six glass-fronted wooden grain storage bins filled with 7.2 kg of shelled corn at 14% moisture content. An auger plug containing a heavily sporulating culture of Aspergillus flavus Link was added to the center of three infested bins and three noninfested bins. Another three bins of corn were untreated controls. All of the bins were stored for 16 weeks at 24°C. Weevil-infested corn began significantly heating (2°C) within nine weeks and began losing weight within 12 weeks. The distribution of fungal growth, high moisture grain, corn dust caking, and maize weevils coincided, being initially restricted to the lower edges of the containers and gradually migrating upward. An unidentified species of Penicillium (bright blue) was observed sporulating within 11 weeks in weevil-infested bins. The bins containing S. zeamais lost an average of 2% of their initial wet weight, and increased in grain moisture and temperature by 20% and 5°C, respectively. Pencillium (bright blue) comprised > 95% of the inoculum present on kernels, however A. flavus comprised > 90% of the inoculum recovered from surface sterilized maize weevils. Increased mortality of teneral adults occurred in A. flavus-inoculated bins. Corn from weevil-free bins, whether inoculated with A. flavus or not, failed to support fungal growth, heat, or lose weight.