The capacity of 3 stored product insect species to vector microbes after increasing dispersal periods.

Abstract

Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), and Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) are 3 important stored product pests of maize, but there has been little work evaluating how they vector microbes. While there has been some work assessing the microbial ecology of S. zeamais, none has directly assessed whether they transfer microbes to new food patches. Thus, we evaluated the ability of both species to vector microbes when given the opportunity to forage on sterilized potato dextrose agar dishes after a 0, 24, or 72 h dispersal period in a sterilized container. We subsequently photographed the dishes at 3 and 5 d after introduction and quantified the microbial growth using ImageJ. In addition, we isolated unique morphotypes of fungi, extracted DNA and amplified the internal transcribed spacer 5/4 intergenic spacer region, then sequenced to determine fungal identity. We found that 3 species readily vectored several plant pathogenic microbes, including 21 taxa from more than 11 genera, notably Aspergillus spp. Increasing dispersal period (0, 24, 72 h) resulted in a third less microbial growth (mean microbial growth or mean greyscale value from 0 to 255) by S. zeamais after 72 h, while for P. truncatus it resulted in a 2.7-fold increase in microbial growth. Dispersal by S. zeamais (0, 24, 72 h) resulted in 6.6-fold more microbial growth than dispersal by P. truncatus. There was 1.5- to 3.7-fold more microbial growth after 5 d than 3 d by each species. This research has important implications for food safety in the postharvest environment, especially for maize production, storage, and processing.