Variation in enantiospecific attraction of Ips avulsus (Coleoptera: Curculionidae) to the pheromone ipsdienol in Georgia

In 2006, we tested the responses of the small southern pine engraver, Ips avulsus (Eichhoff) (Coleoptera: Curculionidae), to multiple-funnel traps baited with (+)-, (-)-, and (+/-)-ipsdienol. Three experiments were conducted in Georgia with all traps co-baited with one of the following lure combinations, respectively: experiment 1, ipsenol; experiment 2, lanierone and (-)-alpha-pinene; and experiment 3, ipsenol, lanierone, and (-)-alpha-pinene. Ipsdienol and lanierone are aggregation pheromones used by I. avulsus, whereas ipsenol is an aggregation pheromone used by the eastern fivespined ips, Ips grandicollis (Eichhoff), a sympatric species also breeding in pines. In all experiments, the highest catches of I. avulsus were obtained in traps baited with (+/-)-ipsdienol. The relative attractiveness of (+)-ipsdienol varied across the three experiments. When traps were co-baited with ipsenol, lanierone, and (-)-alpha-pinene, catches of I. avulsus in traps baited with (+)-ipsdienol were high and no different from those in traps baited with (+/-)-ipsdienol. When traps were co-baited with lanierone and (-)-alpha-pinene, catches in traps baited with (+)-ipsdienol were lower than those in traps baited with (+/-)-ipsdienol by approximately 40%, whereas catches were reduced by approximately 95% when traps were co-baited with ipsenol alone. We hypothesize that the observed variation in enantiospecific responses of I. avulsus to ipsdienol may be explained by variation in semiochemical context (i.e., different co-baits among the experiments) or seasonal variation.