Essential oils as potential insecticides and behavior-modifying agents against <i>Bactrocera tryoni</i> (Diptera: Tephritidae)

The Queensland fruit fly (Q-fly) Bactrocera tryoni is the most economically destructive tephritid pest in eastern Australia, inflicting substantial damage to diverse fruit and vegetable crops. Broad-spectrum, persistent, synthetic insecticides have been used to manage tephritid fruit flies. However, the adverse effects of these insecticides on human health, the environment, and nontarget organisms, as well as regulatory restrictions, have prompted the search for alternative control methods. This study explores the potential of essential oils as alternatives by evaluating their toxicity and behavior-modifying properties against adult Queensland fruit flies. We evaluated 16 essential oils for contact and fumigation toxicity, oviposition inhibition, and repellence. The chemical profiles of the essential oils were analyzed with Gas Chromatography-Mass Spectrometry and antennal responses were assessed by gas chromatography-electroantennographic detection. Chamomile, lemon-scented tea tree, and citronella exhibited notable contact toxicity (ED50 0.054 to 0.068 mg/µl) after a 24-h exposure, while garlic, aniseed, pennyroyal, basil, and peppermint exhibited high fumigation toxicity (ED50 3.293 to 4.950 µl/liter air) over the same period. Aniseed, cumin, and pennyroyal essential oils repelled both Queensland fruit fly sexes in 4-arm olfactometer assay. Aniseed, basil, chamomile, citronella, cumin, dill, garlic, lemon-scented tea tree, pennyroyal, peppermint, thyme, and yarrow essential oils inhibited oviposition. This study demonstrates essential oils as toxicants, oviposition deterrents and repellents, offering promising alternatives to conventional pest control methods for managing Queensland fruit fly populations.