Herbivory-induced long-chain hydrocarbons of legumes influence settlement behaviour of Bemisia tabaci

Plant-derived semiochemicals play an important role in sustainable pest management by influencing insect host selection and feeding behaviour. This study investigated whether herbivory by Bemisia tabaci induces changes in herbivory-associated long-chain hydrocarbons of legume hosts and whether these compounds influence whitefly settlement behaviour. Soybean ( Glycine max ), green gram ( Vigna radiata ), black gram ( Vigna mungo ), and cowpea ( Vigna unguiculata ) were exposed to whitefly infestation under controlled conditions. Comparative dynamic headspace GC–MS profiling revealed herbivory-associated increases in the relative abundance of several herbivory-associated long-chain hydrocarbons, particularly eicosane, heneicosane, tetracosane, dotriacontane, and squalane, although the magnitude of induction varied among host species. Based on these chemical profiles, selected hydrocarbons and structurally related compounds were evaluated in no-choice and choice behavioural bioassays. Several hydrocarbons significantly reduced adult whitefly settlement in a concentration-dependent manner. Among the compounds evaluated, eicosane and squalane consistently exhibited the strongest deterrent activity, reducing settlement by more than 50% under no-choice conditions and by up to 83% under choice conditions. Reduced whitefly settlement remained evident for up to 48 h after treatment. The observed behavioural responses are consistent with the hypothesis that these low-volatility, hydrophobic hydrocarbons may function as contact-associated behavioural cues, although the underlying sensory mechanisms require further investigation. Overall, the findings demonstrate that herbivory-associated changes in herbivory-associated long-chain hydrocarbons are associated with altered whitefly settlement behaviour and identify these compounds as promising candidate semiochemicals for sustainable management of phloem-feeding insect pests, pending quantitative validation and field evaluation.