Estragole, a potential attractant of the winged melon aphid Aphis gossypii.

BACKGROUND: Aphids are sap-sucking insect pests of economic importance. They exhibit polyphenism, producing two kinds of morphotypes; winged (alate) and wingless (aptera) morphs. While wingless morphs can be controlled by insecticides, winged morphs are a challenge for targeted control measures as they can fly. Although colored sticky traps are used to control and monitor winged aphids, only a small population is trapped, making sticky traps less effective in controlling aphids. Studies have shown that fragrant oils applied to sticky traps increased attraction of sap-sucking insects like whiteflies and thrips. Here, we tested selected essential oils for their attractiveness to winged Aphis gossypii in potato fields. RESULTS: In field assays, selected essential oils with yellow or colorless sticky traps attracted more winged A. gossypii than controls. The combination of yellow traps baited with essential oils attracted ~2-3-fold more winged A. gossypii than did colorless traps baited with essential oils. In a multi-cycle 2 year study, yellow sticky traps baited with basil oil consistently attracted more winged A. gossypii than yellow sticky traps baited with lavender, geranium or tea tree oils. In electrophysiological studies, winged A. gossypii's antennae responded consistently to estragole in basil oil. In olfactometer assays with estragole, winged A. gossypii spent significantly more time in the treatment arm of the olfactometer than in the control arm, validating estragole's attractiveness. Furthermore, yellow sticky traps baited with pure estragole, in potato fields, attracted similar number of winged A. gossypii as yellow sticky traps baited with basil oil. CONCLUSION: Our findings demonstrate the potential of using basil oil as a potential attractant to improve the efficacy of sticky traps in the monitoring and control of winged aphids. © 2023 Society of Chemical Industry.

Is the Natural Instinct to Oviposit in Mated Female Oriental Fruit Fly, Bactrocera dorsalis More of a Brain-Independent Act?

What physiological and neuro-molecular changes control the female oviposition behavior post-mating in insects? The molecular changes that occur in a gravid female insect are difficult to dissect out considering the distinct behavioral patterns displayed by different insect groups. To understand the role of the brain center in Oriental fruit fly, Bactrocera dorsalis oviposition, egg-laying behavior was analyzed in γ-octalactone exposed, decapitated mated B. dorsalis females. Interestingly, the females displayed a possible urge to oviposit, which suggests a natural instinct to pass on the gene pool. Expression analysis of certain genes involved in oviposition behavior was also carried out in these insects to explore the molecular aspects of such behavior. This study tries to assess the involvement of brain center in egg-laying and also explore the role of certain neurotransmitter-related receptors in decapitated B. dorsalis oviposition behavior. Our results indicate that B. dorsalis oviposition behavior could potentially have a bypass route of neuronal control devoid of the brain. The study reported here establishes that decapitation in gravid females fails to abolish their ability to sense ovipositional cues and also to oviposit.