A SIMPLIFIED TREE BAIT FOR THE MOUNTAIN PINE-BEETLE

Seven, split-block experiments throughout British Columbia in 1989 tes ted the efficacy of binary tree baits containing the pheromones trans- verbenol and exo-brevicomin or ternary baits with the addition of the host tree kairomone myrcene for containing and concentrating infestati ons of the mountain pine beetle, Dendroctonus ponderosae Hopkins, in s tands of lodgepole pine, Pinus contorta var. latifolia Engelm. Attack densities on baited trees, attack frequencies of baited trees and tree s within 10 m of the baited trees, and the ratios of newly attacked, g reen, trees to previously attacked, red, trees were generally statisti cally equal between sub-blocks containing binary or ternary baits. Whe re statistically significant differences occurred for one or more of t he above criteria in one experiment, they were generally offset by sta tistically significant differences in the opposite direction in anothe r experiment. Two individual-tree experiments in 1990 that supported t he equality of binary and ternary baits indicated that raising the rel ease rate of trans-verbenol in binary baits tended to reduce their eff icacy (possibly because of contamination with the antiaggregation pher omone verbenone) and showed that increasing the release rate of exo-br evicomin tended to counteract this effect. When attack frequencies wer e subdivided by diameter class of available trees attacked, all baits were effective in inducing attack on available trees <30.0 cm diameter at breast height (1.3 m), but attack on baited and control trees grea ter-than-or-equal-to 30 cm diameter at breast height was equal. Provid ed that the transverbenol in binary baits does not contain or autoxidi ze to verbenone, myrcene can be deleted from operational tree baits.