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1‐Methyl‐2‐cyclohexen‐1‐ol (MCOL) was shown for the first time to occur in the frass produced by female spruce beetles, Dendroctonus rufipennis (Kirby). MCOL and 4‐methylene‐6,6‐dimethylbicyclo[3.1.1]hept‐2‐ene (verbenene) were evaluated in five geographic locations for attractiveness to spruce beetles. In trapping experiments (±)‐ or (+)‐ MCOL enhanced attraction to a standard blend of α‐pinene with frontalin in two Alaska locations. (+)‐MCOL was attractive and (‐)‐MCOL inhibitory in south‐central British Columbia, and (+)‐, (‐)‐ and (±)‐MCOL were all weakly attractive in one of three experiments in southeastern British Columbia and northern Alberta. Verbenene was attractive only in combination with the standard blend plus MCOL in Alaska. In comparison with the standard bait, tree baits incorporating (±)‐ or (+)‐MCOL caused higher numbers of trees to be attacked in the interior Alaska locations and (+)‐ MCOL had the same effect in south‐central British Columbia. Density of attack on attacked trees was unaffected. (±)‐ or (+)‐MCOL could improve the operational efficacy of tree baits in Alaska, and (+)‐MCOL could be used in south‐central British Columbia. Our results indicate that for wide‐ranging scolytid species, operational evaluation of new semiochemicals should be regionally specific.

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Direct solar radiation to the bark surface of white spruce, Piceaglauca (Moench) Voss, is the primary environmental factor influencing the developmental rate of spruce beetles, Dendroctonusrufipennis (Kirby), in Alaska. A phloem threshold temperature of 16.5 °C is required to initiate the development of 1 year life cycle beetles. Tree location within a stand and stand aspect in relation to direct solar radiation determine which trees or areas of the tree support beetles with 1- and 2-year life cycles. Two-year cycles normally developed on the north and west sides of standing trees and the north and bottom sides of felled trees, which were characterized by an average phloem temperature of 10.6 °C. One-year cycles normally developed on the south sides of standing trees and the south and top sides of felled trees, which were characterized by an average phloem temperature of 16.5 °C.

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