Flour beetle responses to volatile organic compounds from uninfested and previously infested wheat flour

Insect-mediated changes in volatile organic compounds (VOCs) within grain products can trigger a cascade of effects that either deter or promote subsequent infestation. These semiochemical cues hold promise for developing behavior-based monitoring pest infestation levels and management strategies. This study tested the hypothesis that wheat flour with a history of Tribolium castaneum infestation alters insect preference and development through specific semiochemicals generated or depleted during prior colonization. Significant differences in VOC profiles were detected between uninfested and previously infested flour. Key compounds such as sucrose, ethyl linoleate, phthalic acid ester, and N-(2-hydroxyethyl) decanamide appeared exclusively in uninfested flour, while hexadecenoic acid, linoelaidic acid, and 11-methylpentacosane were unique to beetle-infested flour. Biological assays revealed that uninfested flour supported greater consumption, food conversion efficiency, insect growth, reproduction, and flour loss compared to infested flour. However, no significant difference in initial insect preference between the two substrates was observed. Results suggest that certain VOCs found in uninfested flour may reduce initial attraction but promote consumption, whereas VOCs unique to infested flour enhance colonization preference but suppress feeding. Importantly, substrate preference alone does not predict consumption, which is the key driver of insect development, progeny production, and wheat flour degradation. These findings deepen our understanding of flour beetle-chemical interactions and provide a foundation for targeted pest control strategies based on VOC manipulation.