Cotton Fleahopper Herbivory on Cotton Squares Induces Plant Volatile Emissions that Repel Conspecifics.

The cotton fleahopper, Pseudatomoscelis seriatus, is a piercing-sucking insect that feeds on several plant species, including squares (pre-floral buds) of upland cotton, Gossypium hirsutum, causing square abscission and yield reductions. Current control of cotton fleahoppers relies on pesticide applications, but there is growing interest in using chemical ecology to develop more sustainable methods for integrated pest management. Herbivore foraging behavior is often mediated by plant-produced volatile organic compounds (VOCs), which can serve as attractants or repellants during host-plant selection. This study aimed to evaluate the influence of cotton fleahopper herbivory on VOC emissions from cotton squares under field conditions and to investigate the behavioral responses of conspecific insects to these VOCs. Using dynamic headspace sampling, we identified seven VOCs emitted from cotton squares, with three compounds emitted in higher abundance following cotton fleahopper herbivory: (E)-β-ocimene, (E)-β-caryophyllene, and (E)-β-farnesene. The total emission of VOCs from squares with cotton fleahopper herbivory was greater than non-damaged (control) cotton squares. Using dual choice olfactometer assays, we found that adult cotton fleahoppers preferred VOCs from non-damaged squares compared to VOCs from squares with conspecific herbivory. Furthermore, cotton fleahoppers were attracted to synthetic (E)-β-ocimene but repelled by synthetic (E)-β-caryophyllene or the combination of (E)-β-ocimene and (E)-β-caryophyllene. Our findings suggest that cotton VOCs influence cotton fleahopper foraging, and that compounds identified in this study have potential for development as lures or repellants to use in integrated pest management.