Field evaluations of potential aggregation inhibitors for the southern pine beetle, Dendroctonus frontalis (Coleoptera: Curculionidae)
Semiochemicals that inhibit the response of the southern pine beetle, Dendroctonus frontalis Zimmermann, to its aggregation pheromone have been used with varying degrees of success to protect individual trees from attack and to stop infestation growth. However, semiochemical disruptants have not experienced wide use in management of D. frontalis, due in part to the normally prohibitive expense associated with treatments using verbenone and Callylanisole, the two EPA-registered semiochemicals for this species. Therefore, we conducted some initial trap-based screenings of candidate compounds with the aim of discovering alternative inhibitory semiochemicals for use in management of D. frontalis. In separate experiments in Mississippi and Georgia, baits containing either 2-phenylethanol or myrtenol significantly reduced attraction of one or both sexes of D. frontalis to traps baited with a standard attractant (i.e., the D. frontalis aggregation pheromone frontalin and the host monoterpene alpha-pinene). In combination, the two compounds caused a 92% decrease in total beetle response to the standard attractant, although this reduction was not significantly greater than that produced by 2-phenylethanol alone. In one test, a blend of nonhost volatiles (1-hexanol, cis-3-hexen-1-ol, hexanal, and nonanal) significantly reduced attraction of male D. frontalis, but these observations were not duplicated in a second test. Another combination of candidate inhibitors (the nonhost blend plus guaiacol and benzaldehyde) also significantly inhibited response of male beetles. At the specific doses used in our tests, we failed to observe reduction in D. frontalis attraction by the following compounds presented singly: benzaldehyde, guaiacol, 3-methylcyclohex- 2-en-1-one (3,2-MCH), myrtenal, and verbenone.