The response of four braconid parasitoid species to methyl eugenol: Optimization of a biocontrol tactic to suppress Bactrocera dorsalis

Methyl eugenol (ME) is the most common tephritid male lure used in studies investigating Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), a highly destructive pest species. The following four species of braconid wasps (Hymenoptera: Braconidae) are parasites of several Tephritidae flies of economic significance: Fopius arisanus (Sonan), F. vandenboschi (Fullaway), Diachasmimorpha longicaudata (Ashmead) and Psyttalia incisi (Silvestri). An integrated pest management (IPM) strategy involving the release of multiple parasitoid species, the release of sterile males, and the placement of ME-lure traps was recently implemented in southern China. This study evaluated the effects of ME on braconid parasitoids. Based on the results from olfactometer bioassays, all parasitoid species were significantly repelled by undiluted ME. Furthermore, attractant-influenced behavioral activities occurred at relatively low concentrations of ME (e.g., 0.01, 0.1, and 1 mu l/ml), whereas the effects of the repellent increased to significant levels as the concentration increased. There were no significant differences in electroantennogram (EAG) responses among different doses of ME, but the number of F. arisanus parasitoids attracted to traps containing host eggs decreased significantly at higher concentrations, e.g., 10, 100 and 1000 mu l/ml. In addition, the number of F. arisanus females that were attracted to the host egg trap decreased significantly with higher concentrations of ME (10, 100 and 1 mu l/ml). The number of F. arisanus females that exhibited ovipositional behavior in an environment without ME was significantly higher than those with different concentrations of ME. This study improves our understanding of control tactic interactions as well as the optimization of various processes involved in the IPM program.