IPSDIENOL AND LANIERONE INCREASE IPS PINI SAY (COLEOPTERA, SCOLYTIDAE) ATTACK AND BROOD DENSITY IN LODGEPOLE PINE INFESTED BY MOUNTAIN PINE-BEETLE

Attack and emergence of the engraver beetles Ips pini Say and l. latid eas LeConte were measured in lodgepole pine (Pinus contorta var. latif olia Engelm.) naturally attacked by the mountain pine beetle, Dendroct onus ponderosae Hopk., in 1991. Sample trees were baited with the Ips pheromones ipsdienol and lanierone 1 week and 3 weeks after attack by the mountain pine beetle and again the following spring to observe the effects of the timing of bait placement. The densities of attack, egg gallery length, emergence, and hibernation of lps species were measur ed. Ips latidens did not attack either the baited or unbaited trees at breast height until the spring of 1992 and the relatively low emergen ce was not significantly different by treatments. Among the 1991 treat ments, the densities at breast height (1.3 m) of I. pini attack, egg g allery length, adult emergence in the fall of 1991, and numbers of hib ernating adults in the duff were all highest for the 3-week treatment and lowest for the unbaited treatment. Significantly higher densities of beetles emerged and hibernated in the duff on the north sides of tr ees. Ips pini emergence in late summer 1992 from trees additionally ba ited in spring 1992 was significantly higher than for trees baited onl y in fall 1991. The density and temporal distribution of the emergence of both Ips species is discussed in relation to that of the mountain pine beetle.