Synthesis and Field Evaluation of Zingerone Analogues as Attractants for Bactrocera jarvisi
Fruit flies (Diptera: Tephritidae) are amongst the most significant agricultural pests globally and impact numerous crops. Species of fruit flies have been categorised by the attraction or unattraction of male flies to male-specific chemical attractants or lures, especially methyl eugenol and cuelure. Zingerone is a unique male lure possessing structural features of both methyl eugenol and cuelure, and is known to attract both methyl eugenol and cuelure responsive species, as well as some species that are weakly or non-responsive to these existing lures. In Australia, Bactrocera jarvisi (Tryon) is one such lure non-responsive species that is only very weakly attracted to cuelure and not attracted to methyl eugenol but is strongly attracted to zingerone. However, the key features of zingerone that mediate this attraction are unknown. In this project, analogues of zingerone were synthesised and the response of B. jarvisi to 3 7 analogues was evaluated primarily through field trials, which established that the most attractive analogues were alkoxy derivatives with isopropoxy being the most attractive, followed by ethoxy and trifluoromethoxy analogues. Larger alkoxy groups were unattractive, which suggested that the receptor cannot accommodate alkoxy groups greater than two carbons in length or bulkier than an isopropoxy group. Another attractive group of analogues were the phenolic esters, all of which were attractive with the response decreasing with increasing size of the ester, except for a fluorinated ester. Increasing the steric bulk around the butanone side chain through methylation tended to eliminate attraction with only methylation of the benzene ring side of the ketone yielding a moderately attractive analogue. These results demonstrate that the carbonyl group, phenol, and methoxy group are key sites for the attraction of B. jarvisi and identify some constraints on the range of structural modifications that can be made to zingerone without compromising attraction.