Abstract
The peach fruit fly (PFF) Bactrocera zonata (Diptera: Tephritidae) is a major agricultural pest attacking at least 55 plants of economic importance. Previous studies have identified unique compounds in each sex, but none of these appear attractive to either sex. However, it is well known that methyl eugenol (ME) found in nectaries of many plants is strongly attractive to males, while food baits are weakly attractive to both sexes. The present study was designed to find repellent substances for the PFF to implement “push-pull” methods as part of efforts to control the pest and protect orchards. The push-pull method requires an attractant, such as ME, for the fly, and a repellent, which has yet to be discovered. A substance is repellent if it can reduce the attraction of insects to a trap with an attractant as compared to a trap with an attractant alone. The reduction is measured as “trap shutdown”, with 100% shutdown being complete repulsion. After systematically screening 82 commercial essential oils (EOs) presented in combinations in field experiments, we found that two EOs, Yarrow and Ylang-ylang, caused over 95% trap shutdown for PFF males and females at different timings and in different orchards (i.e., citrus and mango). We also tested the components of these two EOs and found that artemisia ketone, a component of Yarrow EO, causes a significant trap shutdown of 98% for males and 92% for females. Each component of Ylang-ylang EO tested in the field did not give a sufficient shutdown, suggesting possible synergism among components. However, this EO is inexpensive and thus can be applied wholly in a suitable formulation. We believe that our findings could be developed for the push-pull of other fruit flies known to be attracted to ME.