Active ingredients in cade oil that synergize attractiveness of alpha-ionol to male Bactrocera latifrons (Diptera: Tephritidae)

Cade oil, a commercially available essential oil produced by destructive distillation of juniper, Juniperus oxycedrus L., twigs, is known to synergize the attractancy of alpha-ionol to male Bactrocera latifrons (Hendel). Through chemical fractionation and outdoor olfactometer-based bioassays, seven compounds in cade oil were identified that potentially could provide some level of synergism. Tests with sterile laboratory flies showed that four of the seven compounds (eugenol, isoeugenol, 2-methoxy-4-ethylphenol, and 2-methoxy-4-propylphenol), together with a closely related compound not found in cade oil, 2-methoxy-4-methylphenol, are capable of synergizing the attractiveness of alpha-ionol to male B. latifrons under field conditions. The similarity in structures of these five synergistic compounds shows that there is a response to a core 2-methoxyphenol structure, with fly response little affected by some variation in the composition of the side chain on the number 4 carbon. Because identified synergists were structurally similar, only one compound, eugenol, was selected for further field studies. In an 8-wk weathering test, using released sterile flies, traps baited with alpha-ionol + eugenol had catches comparable with catches at traps baited with alpha-ionol + cade oil, with catches generally increased with a higher eugenol loading. For both eugenol and cade oil, catches tended to be better when these synergists were deployed on separate wicks from the alpha-ionol. Eugenol and alpha-ionol, however, were unable to provide attraction comparable with that of cade oil and alpha-ionol in tests with wild fly populations.