Identification of a host compound and its practical applications: 4-allylanisole as a bark beetle repellent
Gas chromatography/mass spectometry analysis of resin collected before and after injections of loblolly pines (Pinus taeda L.) with a fungicide mixture known to make pines more "attractive" to southern pine beetle, Dendroctonus frontalis Zimm., resulted in the identification of 4-allylanisole as a likely candidate for repellent effects. The phenylpropanoid, 4-allylanisole (Chemical Abstract 140-67-0), is a compound produced by many conifers, including loblolly pine, an abundant species in southern pine forests and a preferred host of the southern pine beetle.The repellency of 4-allylanisole to southern pine beetle was demonstrated in laboratory behavioral assays and in natural populations by comparing its effects with those of the beetle-produced inhibitory pheromone, verbenone. Responses by other North American scolytids and associates were also determine. Additionally, responses of southern pine beetle to various chemical analogues of 4-allylanisole were tested.The response in the field of southern pine beetle to its attractant pheromone in funnel traps was significantly reduced by simultaneous release of either 4-allylanisole or verbenone, which did not differ from one another in repellency.Both compounds together did not significantly further reduce trap catch. The response of a major predator, Thanasimus dubius (F.), to the attractant pheromone of southern pine beetle did not differ with the simultaneous release of either compound.The results of preliminary field test with 4-allyanisole, in which lightning-struck pines were protected from southern pine beetle attack, are presented and discussed in relation to implications for development of a practical tree protection tactic.