Repellency and oviposition deterrence effects of plant essential and vegetable oils against female Queensland fruit fly Bactrocera tryoni (Froggatt) (Diptera: Tephritidae)

Eight plant essential oils and five vegetable oils were evaluated under laboratory conditions for their repellency and oviposition deterrence effects against female Queensland fruit fly Bactrocera tryoni, using artificial substrates and apple fruits. The results showed that vegetable oils were more effective than essential oils in deterring oviposition. The oil with most potential was that of safflower Carthamus tinctorius. This vegetable oil, at a concentration of 10mL/L, significantly reduced oviposition in apples by 56.4% in a 24h choice test, but none of the tested essential and vegetable oils had a significant effect on oviposition in apples in a no-choice test. Based on the number of fruit flies landing on treated apples, vegetable oils were not repellents but deterred oviposition. The likely mechanism is that safflower and other vegetable oils created a slippery surface, and females were unable to make punctures in the fruit for egg deposition. Essential oils, especially lemon-scented tea tree Leptospermum petersonii, peppermint Mentha piperita and honey myrtle Melaleuca teretifolia, repelled female B.tryoni, but their persistence on apple fruits was very low, only for a few hours.