Longevity of pheromone and co-attractant lures used in attract-and-kill stations for control of Carpophilus spp

Field longevity of synthetic lures for Carpophilus spp. (Coleoptera: Nitidulidae) was evaluated by trapping studies in Australia, accompanied by chemical analyses. Carpophilus spp. are serious pests of ripening fruits, and an attract-and-kill method has been developed for their control. Traps are baited with one of two types of lure: synthetic pheromone (in rubber septa) and a host-related synthetic co-attractant (as an aqueous solution). No information was available on the longevity of either lure type. The objective of the study was to understand changes in attractiveness of the pheromone septa and co-attractant over time under field conditions. Pheromone septa were still attractive after 28 days in the field, but activity declined over time. Relative to fresh septa, catches in traps baited only with the pheromone declined to 75, 53, 32, 21, and 16% for 3-, 7-, 14-, 21-, and 28-day-old septa, respectively. Chemical emissions from aged septa showed a very similar decrease with time. Trap catches when both pheromone and co-attractant were present were far higher, and the decrease as the pheromone aged was less rapid (catches were 87, 73, 55, 44, and 36% of the original level for 3-, 7-, 14-, 21-, and 28-day-old septa, respectively). Apparently the presence of co-attractant could partially compensate for the deterioration of pheromone septa. The chemical changes of the co-attractant decreased more rapidly than the pheromone. In a laboratory study, two minor components (acetaldehyde and ethyl acetate) were essentially gone after 1 day, while the major component (ethanol) and the other three minor components (2-methyl-1-propanol, 3-methyl-1-butanol, and 2-methyl-1-butanol) were detectable for up to 4-8 days. Co-attractant evaporation was somewhat slower under field conditions. Trap catches for co-attractant of various ages and pheromones decreased three-fold as co-attractant age increased from 0 to 14 days. Implications with respect to beetle control are discussed.