4-ALLYLANISOLE AS AN INHIBITOR OF BARK BEETLE (COLEOPTERA, SCOLYTIDAE) AGGREGATION

To assess the extent of inhibitory activity of the host compound 4-all ylanisole, we conducted field studies with three scolytid species. The se species are geographically widespread and economically important. T rials were completed with Dendroctonus brevicomis LeConte (California) , D. ponderosae Hopkins (Oregon), and Ips pini (Say) (Wisconsin) by us ing multiple-funnel traps with appropriate pheromone-based attractants . With the Dendroctonus species, the effects of 4-allylanisole were co mpared with verbenone, an aggregation inhibitor produced by beetles th emselves. We also determined effects of the treatments on the most abu ndant coleopterous predators in each trial. Inhibition of bark beetle aggregation behavior by 4-allylanisole was demonstrated for D. pondero sae (Oregon) and I. pini (Wisconsin). In Oregon, 4-allylanisole reduce d the catch of D. ponderosae at attractant-baited traps by 77%, wherea s verbenone reduced the catch by 91% compared with attractant alone. A lthough both reductions were significant, the effect of verbenone was significantly greater than that of 4-allylanisole. In Wisconsin, addit ion of 4-allylanisole to attractant-baited traps resulted in a signifi cant reduction (43%) in numbers of I. pini caught, compared with attra ctant alone. In the California trials, mean trap catches of D. brevico mis were reduced by both 4-allylanisole (35%) and verbenone (27%) comp ared with attractant alone, but neither reduction was significant. Sex ratios of target scolytids were not affected by inhibitory treatments in any trial. The predator Temnochila chlorodia (Mannerheim) (Coleopt era: Trogositidae) was not affected by 4-allylanisole in California; h owever, verbenone significantly reduced the number caught. Although ca ptures were low, numbers of T. chlorodia caught by traps containing 4- allylanisole in Oregon were significantly higher than those containing verbenone or attractant alone (numbers in verbenone and attractant tr aps were not significantly different). Numbers of the predatory beetle s counted in Wisconsin-Thanasimus dubius (F.) (Coleoptera: Cleridae), Platysoma parallelum Say (Coleoptera: Histeridae), and P. (Cylistix) c ylindrica (Paykull) (Coleoptera: Histeridae)-were not affected by elut ion of 4-allylanisole with the attractant. Implications of these resul ts for protection of individual trees and management of bark beetle po pulations are discussed.