A Systematic Review of the Behavioral Responses by Stored-Product Arthropods to Individual or Blends of Microbially Produced Volatile Cues

SIMPLE SUMMARY: Microbes are everywhere, including in our food after harvest. Stored-product arthropods have been described as attracted, repelled, or unaffected by microbial cues in the prior published literature, but no one has systematically examined all the prior tests to determine general patterns. We reviewed 43 articles that contained 384 sets of tests on 24 stored-product arthropod species, classifying each response as positive, negative, or net neutral (unaffected or mixed). A total of five and four stored-product arthropods were significantly attracted and repelled by microbial cues, respectively, while 13 were unaffected or exhibited attraction and repellency. We found that the behavioral responses by stored-product arthropods to microbial cues were complex, context-, and species-dependent, which warrants further investigation to clarify mechanisms. ABSTRACT: Microbes are ubiquitous and play important ecological roles in a variety of habitats. While research has been largely focused on arthropods and microbes separately in the post-harvest supply chain, less attention has been paid to their interactions with each other. Up to this point, there has been no attempt to systematically describe the patterns of behavioral responses by stored-product insects to microbially produced volatile organic compounds (MVOCs). Thus, our aims were to evaluate whether stored-product arthropods were primarily and significantly attracted, repelled, or had a net neutral effect (e.g., unaffected or mixed) by MVOCs presented as (1) complex headspace blends or (2) single constituents and known mixtures. In total, we found 43 articles that contained 384 sets of tests with different combinations of methodology and/or qualitative findings, describing the behavioral responses of 24 stored-product arthropod species from two classes, four orders, and 14 families to 58 individual microbial compounds and the complex headspace blends from at least 78 microbial taxa. A total of five and four stored-product arthropod species were significantly attracted and repelled by MVOCs across odor sources, respectively, while 13 were unaffected or exhibited mixed effects. We summarize the biases in the literature, including that the majority of tests have occurred in the laboratory with a limited subset of methodology and has largely only assessed the preference of adult arthropods. Finally, we identify foundational hypotheses for the roles that MVOCs play for stored-product arthropods as well as gaps in research and future directions, while highlighting that the behavioral responses to MVOCs are complex, context-, and taxon-dependent, which warrants further investigation.