Exogenous application of dehydrocostus lactone induces volatile emission in cotton and enhances settling and oviposition by Bemisia tabaci (Hemiptera: Aleyrodidae)

Abstract Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is an agricultural pest that is increasingly resistant to traditional management strategies. The need for safe, effective, and low-cost control methods has spurred research into Volatile organic compounds (VOCs) produced by plants in response to herbivory. Dehydrocostus lactone (DCL), a sesquiterpene lactone, is a VOC found primarily in the Asteraceae. Here, we applied DCL directly to cotton (Gossypium hirsutum) plants to investigate its impact on the host plant itself and on the herbivorous B. tabaci. Recent studies have shown that whiteflies preferred to settle and oviposit on DCL-sprayed versus control plants. A one-time exposure to DCL had little effect on foliar flavonoids and salicylic acid levels but decreased foliar phenolics by 28% and jasmonic acid by 47% over a 2-week period. Treatment with DCL increased total VOC emissions 10-fold over those of control plants, largely due to increases in the compounds 3, 6, 9, 12-tetraoxatetradecan-1-ol, octaethylene glycol monododecyl ether, and 15-crown-5. Y-tube assays demonstrated that the compound 3, 6, 9, 12-tetraoxatetradecan-1-ol exhibited strong attraction to both male and female B. tabaci at higher concentrations (12.5 to 62.5 µg/ml). Similarly, octaethylene glycol monododecyl etheralso showed strong attractiveness at concentrations of 0.5 µg/ml and 12.5 µg/ml; 15-crown-5 only attracted male whiteflies (0.5 µg/ml, 12.5 µg/ml and 62.5 µg/ml). The fact that DCL suppresses plant defense and induces production of VOCs that attract both male and female B. tabaci provides a solid scientific basis for the development of synthetic attractants for biological control.