Behavior of the pine engraver Ips pini (Say) was observed through plexiglass rearing chambers containing ponderosa pine (Pinus ponderosa Lawson) phloem. Periods of jostling in each entrance tunnel between the resident male and entering female preceded a female’s admission to the nuptial chamber. On the average, mating was completed in 25 seconds. In the gallery, beetles walked on protibial spines, keeping their tarsi folded against their tibiae. Eggs were deposited in niches on either side of the egg gallery and covered by phloem fragments. Larvae mined at right angles to the egg gallery and formed their molting chambers by doubling back and packing frass tightly against that already in the gallery. Larvae consumed their exuviae shortly after molting. Feeding by callow adults on prepupae and pupae may be an important natural control.

Reciprocal field tests of attraction between populations of Ips pini (Say) from California, Idaho, and New York disclosed geographic variation in pheromone systems. These differences reside both in pheromone production and reception. However, it is unknown whether variation in the pheromone bouquets is qualitative, quantitative, or both.In New York, both sexes responded in higher numbers to their own pheromone than that produced by California or Idaho males. In California, beetles of both sexes discriminated against New York, but in Idaho only females made this distinction. In both California and Idaho, the local population showed a slight preference for the pheromone produced by Idaho males over that produced by California males.The predator Enoclerus lecontei (Wolc.) demonstrated a four-fold preference for attractants produced by males from New York over those produced by beetles from California and Idaho. The parasitoid Tomicobia tibialis Ashmead showed the opposite trend.There is no evidence that geographic variation in the pheromones produced by I. pini is sufficient to enforce breeding isolation between adjacent populations. However, these results dramatize the necessity of considering pheromonal variability in programs applying pheromones for the survey and control of widely distributed pests.

Verbenone, a bark beetle antiaggregative pheromone, was deployed in lodgepole pine (Pinuscontorta Dougl. var. latifolia Engelm.) stands in the Sawtooth National Forest, Idaho, U.S.A., to test its efficacy in reducing tree losses to mountain pine beetle (Dendroctonusponderosae Hopkins). Treatments tested were verbenone, mountain pine beetle tree bait, verbenone plus mountain pine beetle tree bait, and a control. Each treatment was applied individually to 1-ha blocks and replicated four times. Treatment effects were measured by percentage of infested (i.e., mass-attacked) lodgepole pine. ANOVA showed a significant treatment effect (P < 0.005). Blocks treated with mountain pine beetle tree baits had significantly (P < 0.002) higher average percentages of infested trees (24.4%), whereas no significant difference occurred in percentages of infested trees among the other three treatments. Average percentages of infested trees were 0.9% for verbenone, 7.4% for verbenone plus mountain pine beetle tree bait, and 3.3% for the control. A 2.3-fold reduction in infested trees occurred when verbenone was applied to blocks treated with mountain pine beetle tree baits.

Attraction of the spruce beetle, Dendroctonus rufipennis (Kirby), to beetle-infested logs was reduced 99% by addition of 3-methyl-2-cyclohexen-1-one (MCH), the natural antiaggregative pheromone of the Douglas-fir beetle, D. pseudotsugae Hopkins. The synthetic attractant frontalin and α-pinene attracted few spruce beetles and its nominal attraction was nearly nullified by addition of MCH. Male spruce beetles responded to the natural and synthetic attractants in greater numbers than females. When MCH was added to these treatments, females predominated among the few beetles caught. The clerid Thanasimus undatulus Say was strongly attracted to treatments containing frontalin, whether or not MCH was added, but MCH alone was not attractive to this predator. Among 13 other species of scolytids caught, the most abundant were Scierus annectens Leconte and Hylastes nigrinus (Mann.). Two relatively rare species, Scierus pubescens Sw. and Xylechinus montanus Blkm., were attracted in unusual numbers to natural spruce beetle attractant. Intensive study is recommended of the possible use of MCH to prevent increase of spruce beetle populations.