The capacity of three laboratory and field-caught stored product insects to vector microbes after foraging at novel food patches

Authors: QUELLHORST, HANNAH - Kansas State University; HOLGUIN ROCHA, ANDRES - Kansas State University; SAKKA, MARIA - University Of Thessaly; TSINTZOU, G - University Of Thessaly; MAILLE, JACQUELINE - Kansas State University; PONCE, MARCO - Orise Fellow; VAGELAS, I - University Of Thessaly; MADESIS, P - University Of Thessaly; ATHANASSIOU, CHRISTOS - University Of Thessaly; Scully, Erin; ZHU, KUN YAN - Kansas State University; Morrison Iii, William

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Larger grain borer and maize weevil are two important stored product pests that infest corn after it is harvested from the field. In addition to causing physical damage to corn by feeding, some stored product insects can vector microbes, which could cause spoilage or introduce toxins that can have consequences for human/animal health and food safety. However, it is not known if larger grain borer and maize weevil can vector microbes from contaminated to uncontaminated food. In this study, we evaluated the ability of both species to vector microbes to new food sources by allowing insects that had recently fed on corn to forage on potato dextrose agar, a microbiological growth substrate, and documenting microbial growth. In addition, insects were held in a sterilized container prior to introducing them to the agar for 0-, 24-, or 72-h to simulate whether increasing dispersal time between the two food sources would influence the amount of microbial growth. We found increasing dispersal time to 27 h resulted in a third less microbial growth by maize weevil and an approximately 3-fold increase in microbial growth for larger grain borer. Overall, dispersing maize weevil resulted in almost 7-fold more microbial growth than larger grain borer. We also found that both species readily vectored several plant pathogenic microbes and two species of mycotoxin-producing fungi, notably Aspergillus and Penicillium. Thus, both species can vector microbes, but microbial growth from maize weevil was higher suggesting that it may pose a higher risk to food safety than larger grain borer. This research has important implications for food safety in the postharvest environment, especially for maize production, storage and processing.

Technical Abstract: Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) and Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) are two 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. However, this has important ramifications for food safety. Thus, we evaluated the ability of both species to vector microbes when given the opportunity to forage on potato dextrose agar dishes (e.g., novel food patch) 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 ITS5/4 intergenic spacer region, then sequenced to determine fungal identity. We found that both species readily vectored several plant pathogenic microbes, including 21 taxa from 11 genera, notably Aspergillus and Penicillium spp. Increasing dispersal period (0, 24, 72 h) resulted in a third less microbial growth 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 resulted in 6.6-fold more microbial growth than dispersal by P. truncatus. There was 1.5–3.7-fold more microbial growth after 5 d than 3d by each species in a novel food patch. This research has important implications for food safety in the postharvest environment, especially for maize production, storage and processing.