4-Allylanisole as an Inhibitor of Bark Beetle (Coleoptera: Scolytidae) Aggregation

Abstract

To assess the extent of inhibitory activity of the host compound 4-allylanisole, we conducted field studies with three scolytid species. These species are geographically widespread and economically important. Trials were completed with Dendroctonus brevicomis LeConte (California), D. ponderosae Hopkins (Oregon), and Ips pini (Say) (Wisconsin) by using multiple-funnel traps with appropriate pheromone-based attractants. With the Dendroctonus species, the effects of 4-allylanisole were compared with verbenone, an aggregation inhibitor produced by beetles themselves. We also determined effects of the treatments on the most abundant coleopterous predators in each trial. Inhibition of bark beetle aggregation behavior by 4-allylanisole was demonstrated for D. ponderosae (Oregon) and I. pini (Wisconsin). In Oregon, 4-allylanisole reduced the catch of D. ponderosae at attractant-baited traps by 77%, whereas verbenone reduced the catch by 91% compared with attractant alone. Although both reductions were significant, the effect of verbenone was significantly greater than that of 4-allylanisole. In Wisconsin, addition of 4-allylanisole to attractant-baited traps resulted in a significant reduction (43%) in numbers of I. pini caught, compared with attractant alone. In the California trials, mean trap catches of D. brevicomis were reduced by both 4-allylanisole (35%) and verbenone (27%) compared 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) (Coleoptera: Trogositidae) was not affected by 4-allylanisole in California; however, verbenone significantly reduced the number caught. Although captures 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 traps were not significantly different). Numbers of the predatory beetles counted in Wisconsin-Thanasimus dubius (F.) (Coleoptera: Cleridae), Platysoma parallelum Say (Coleoptera: Histeridae), and P. (Cylistix) cylindrical (Paykull) (Coleoptera: Histeridae)-were not affected by elution of 4-allylanisole with the attractant. Implications of these results for protection of individual trees and management of bark beetle populations are discussed.