Evaluation of two repellent semiochemicals for disruption of attack by the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae)

Journal of the Entomological Society of British Columbia, Dec 2004 by Borden, John H, Pureswaran, Deepa S, Poirier, Lisa M

Captured beetles in Exp. 1 and 2 were collected on 13 and 26 August, respectively. Beetles were held at ca. -5 °C in plastic bags until sexed and counted.

Tree protection experiments were evaluated on 25-27 September (Exp. 3B and 4B) and 3-4 October (Exp. 3A and 4A). The attack density was counted at eye level in two 20 x 40 cm panels on the east and west faces of baited trees and all trees with at least five attacks in the total 0.16 m^sup 2^ area (31.25/m^sup 2^) were classed as mass-attacked. All surrounding lodgepole pines at least 17.5 cm dbh within 5 m of baited trees were evaluated as unattacked, attacked, or mass-attacked, the latter being determined qualitatively by visual estimation of attack density and copious amounts of frass in bark crevices and around the root collar.

Data for numbers of beetles captured and attack density on baited trees were log-transformed and analyzed by ANOVA and the REGW test (Day and Quinn 1989). Data on proportions of baited and surrounding trees that were mass-attacked were analyzed by chi-square tests for comparison between multiple proportions (Jones 1984). In all cases α = 0.05.

RESULTS

In the first trapping experiment (Exp. 1), MCH, 2-phenyl ethanol and verbenone reduced the catches of male and female mountain pine beetles in attractant-baited traps by 67.4%, 71.8% and 96.6%, and 95.1%, and 97.5% and 97.3%, respectively, relative to catches in baited control traps (Table 1). 2-Phenyl ethanol reduced catches to levels no different from those achieved by verbenone (both sexes) or the ternary blend (males only), but only the latter two treatments resulted in catches not significantly different from those in unbaited control traps. In Exp. 2, all binary combinations and the ternary combination of disruptants reduced catches by more than 96%, and in all cases catches in traps with disruptive treatments were no greater than in unbaited control traps.

In the first tree protection experiment near Princeton (Exp. 3A), all pheromone-baited control trees were mass-attacked (Table 2). MCH and 2-phenyl ethanol alone reduced the proportion of baited trees that were mass-attacked by 16.0% and 33.3%, respectively, but verbenone and the ternary blend completely protected pheromone-baited trees and all trees within 5 m of them from attack. In Exp. 3B near Prince George, only verbenone and the ternary blend significantly reduced the percentage of baited trees that were mass-attacked, and the lowest percentages of surrounding trees that were mass-attacked occurred in the 2-phenyl ethanol and ternary blend treatments.

In the second tree protection experiment near Princeton (Exp. 4A), the binary combination of MCH and 2-phenyl ethanol reduced the percentage of baited trees that were mass-attacked by 40%, but did not cause a reduction in the proportion of surrounding trees that were mass-attacked (Table 2). All treatments containing verbenone reduced attack to zero or to a level not significantly different from zero. In Exp. 4B near Prince George, all treatments significantly and equally reduced the percentage of baited trees that were mass-attacked, but no treatment had a significant effect on attack on surrounding trees.