Can. Ent. 1 1 1 : 1355-1360 (1979) The antiaggregation pheromone MCH was ineffective in preventing spruce beetle infestation in felled spruce near Hope, Alaska. In October, most progeny were larvae but some were pupae and new adults. Densities of spruce beetle attacks and progeny on the shaded under side of stems were about twice those on the upper side, whereas attacks of Polygraphus rufipennis (Kirby) and Dryocoetes affaber (Mann.) on the upper side were 100 times those on the under side. Ips tridens engelmanni Swain was present in only 2% of bark samples. Entomophagous insects were scarce; only Medetera sp. and Coeloides sp. were found. Spruce beetle progeny were 45 times more abundant than attacking parents. Factors affecting the efficiency of sampling spruce beetle attacks and progeny are discussed.The spruce beetle, Dendroctonus rufipennis (Kirby) (= obesus (Mann.) = engelmanni Hopk.), infests mature spruces throughout their distribution in North America. Outbreaks have occurred at numerous locations (Furniss et al. 1976;Schmid and Frye 1977) including the general vicinity of this study (Baker and Kernperman 1974).Completion of a spruce beetle generation requires 1 to 3 years (usually 2),

Can. Enr. 111: 1361Enr. 111: -1368Enr. 111: (1979 Dosage-response relationships of seven insect growth regulators (IGRs) to last instar western spruce budworm, Choristoneura occidentalis Freeman, were determined by topical application, spray application, and diet incorporation bioassays. Mortality was defined as failure to emerge as a viable adult. In spray application experiments, four IGRs-ZR-512, ZR-619, ZR-1662, and Ro 10-3108-had LD,,s of less than 70 g/ha (1 ozlacre). Relative lethal effectiveness, based on a simple model combining data from the three bioassays, was ZR-1662 > ZR-619 > ZR-512 > Ro 10-3108 > ZR-777 > ZR-587 > ZR-515. We concluded that several IGRs, applied to a population consisting primarily of last instars, would induce lethal effects at dosages comparable to dosages of several conventional insecticides.

Variables affecting the efficacy of seven juvenile hormone analogues on western spruce budworm, Choristoneura occidentalis Freeman, were examined in laboratory bioassays. Those tested were epofenonane, hydroprene, kinoprene, methoprene, triprene, ZR-587, and ZR-1662. Selected intrinsic variables—stage of development, sex, and extent of direct contact with sprays—were examined in bioassays involving direct exposure of third instars, direct applications to three pupal age classes, and indirect applications to sixth instars. An extrinsic variable, persistence in the environment, was assessed by determining the residual effectiveness of each juvenile hormone analogue to sixth instars. Sixth instars, rather than third instars, appeared to be the target of choice for two reasons. First, less active ingredient would be required for equivalent mortality by the time of adult eclosion. Second, greater, more consistent, deleterious reproductive effects coupled with a lower incidence of sexual variation in lethal effectiveness, would occur. Pharate pupae and untanned pupae were very susceptible to most of the chemicals and may provide a secondary target for the primary target, sixth instars. The importance of direct chemical-insect contact in achieving maximum reproductive inhibition suggests that these chemicals might be used most effectively in ways such that contact can be maximized, as in ground applications. Finally, some juvenile hormone analogues such as epofenonane and ZR-1662 appeared to persist long enough to permit flexibility with respect to instar distribution in a population.