Sublethal herbicide exposure alters cotton susceptibility to aphid infestation

Herbicides remain vital tools for weed control, yet their effects can extend beyond weeds to affect crop plants, altering plant-insect interactions. Field observations of elevated cotton aphid (Aphis gossypii) infestations following a simulated herbicide drift in cotton suggested that sublethal herbicide exposure might increase crop susceptibility to insect pests. To investigate this phenomenon, multiyear field and glasshouse experiments were conducted to determine whether sublethal herbicide exposures, such as those resulting from off-target drift, modify cotton susceptibility to aphid infestations.

In field studies, sublethal herbicide exposure altered cotton susceptibility to aphids, with herbicide type significantly influencing the extent of infestations. Synthetic auxins (2,4-D and dicamba) were consistently associated with the highest aphid densities, followed by glufosinate and glyphosate, whereas atrazine, paraquat, isoxaflutole and nicosulfuron suppressed or maintained aphid infestations below those of untreated controls. Aphid severity was highest when applications were made during early vegetative stages and declined as the crop matured. In glasshouse experiments, herbicide effects were strongly dose-dependent: moderate exposure promoted aphid proliferation, whereas higher doses suppressed aphid populations. Correlations between crop injury from herbicides, relative chlorophyll content and aphid density indicate that herbicide-associated physiological stress and altered plant vigor influence susceptibility. Spatial analyses revealed higher aphid numbers around auxin-treated plants, suggesting potential drift-related or volatile-mediated influences on aphid behavior or reproduction.

This study provides clear evidence that sublethal herbicide exposure to crops can enhance aphid infestation through stress-induced physiological and ecological mechanisms. By demonstrating consistent, herbicide-specific patterns across field and glasshouse environments, these results highlight the need to incorporate indirect herbicide effects into integrated pest management and ecological risk assessment frameworks. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.