The eastern spruce budworm, Choristoneura fumiferana Clemens, is the most widely distributed and destructive forest insect pest in North America. Although much is known about the ecology, population dynamics, and impact of C. fumiferana on tree growth (Sanders et al. 1985), there is very little information available on the physiology of this forest pest. Physiological studies are crucial to the development of novel strategies for spruce budworm control.

Bacillus thuringiensis (B.t.) + sublethal doses of the organophosphates fenitrothion or Orthene® were aerially applied to spruce budworm infested white spruce and balsam fir trees. B.t. + fenitrothion applied at 10 BIU + 17.5 g active ingredient in 4.71./ha (4 BIU + 0.25 oz in 0.5 gal/acre) and depositing at 1.5 to 3.0 BIU + 2.1 to 4.9 g/ha (0.03 to 0.07 oz/acre) did not protect the trees in the year of application owing to too low application rates but apparently gave good protection 1 year later without further treatment. A B.t. + Orthene combination applied at 20 BIU + 42 g/ha (8 BIU + 0.6 oz/acre) and depositing at the rate of 6.9 BIU + 12.6 g/ha (2.29 BIU + 0.18 oz/acre) provided good protection for both tree species in the year of spray.

Moth emergence was substantially reduced by 20 to 30 BIU B.t. + Orthene combination treatment. Thuricide fenitrothion, Dipel fenitrothion, and 30 BIU Orthene treatments reduced oviposition rate by at least 62%, 47%, and 47%, respectively. B,t. + a low dose of Orthene apparently had no major destructive effects on larval, pupal, or egg parasites whereas B.t. + a low dose of fenitrothion seriously reduced egg parasitism.

The data indicate the possibility of using B.t. in combination with low doses of chemical insecticides against the spruce budworm as an alternative to high doses of chemical insecticides alone.

A series of laboratory toxicological experiments using various concentrations of oil formulated DDT solutions (AR-50/fuel oil (2:7 V/V)) was carried out on 5th and 6th instar spruce budworm larvae collected in the field from DDT-sprayed and untreated areas of New Brunswick, Canada, and Maine, U.S.A.

Results obtained in 1959, 1961, and 1962 with larvae collected from isolated, unsprayed areas in New Brunswick showed a consistent, straight log-dosage probit mortality curve. Larvae collected in 1962 and 1963 from infestation centres previously subjected to three, four, and five applications of non-consecutive large-scale aerial sprays of DDT showed a significant departure from the straight log-dosage probit curve previously obtained. The departure occurs as a change in the shape of the curve as well as a shift to the higher concentration range of DDT. The magnitude of change appears to be correlated with the number of sprays to which the population was exposed. Results obtained in 1962 and 1963, from untreated control and inter-spray areas, bounded by DDT-sprayed forest lands, showed a small but significant departure from the normal straight probit line of a susceptible population. These changes are indicative of a progressive development of DDT resistance in wild populations of spruce budworm.

Studies on the effect of the tolerance of spruce budworm larvae within instar classes to the action of DDT showed that the early phase of instar development immediately after moulting is more susceptible to the action of DDT, whereas the latter phase of instar development immediately prior to moulting is more tolerant to topical application of DDT than the average for the instar. This effect is evident in both susceptible and resistant populations.

The data interpretation assumes that a deviation from the straight line probit dosage – mortality curve is indicative of a difference in the DDT-susceptibility factor of the budworm population and that in the course of the tests, the amount of toxicant causing mortality was not proportional to the dosage.

A reinvestigation of the sex pheromone of the eastern spruce bud worm, Choristoneura fumiferana (Clem.), showed that it contains 11-tetradecenal in the ratio 96% trans-: 4% cis-. Field trapping showed the pure trans- compound to be only slightly attractive. Maximum attraction occurred in the range 2% to 5% cis-.

Well-fed, mated female spruce budworm (Choristoneura fumiferana (Clem.)) show little activity during the first 24 h after emergence. During the second 24 h they lay between 33 and 50% of their egg complement. During the third 24 h most flight activity occurs. Smaller, artificially starved females are much more active, especially during the second 24-h period, when many fly before ovipositing. Timing of oviposition and flight is under photoperiodic control: female flight occurs just before dark after peak oviposition while male activity starts before dark, but peaks after dark, with a morning peak of variable intensity.

The major component of the sex pheromone of the eastern spruce budwonn was established by Weatherston et al. (1971) to be trans-11-tetradecenal. Subsequently it was found (Sanders and Weatherston 1976) that a small proportion of cis-11-tetradecenal was essential to attraction and indeed was a component of the natural pheromone. In addition Weatherston and Maclean (1974) have shown that the female sex pheromone gland contains trans-11-tetradecenol, a presumed biosynthetic precursor to the aldehyde.

Trichogramma minutum Riley was released in the field for suppression of epidemic spruce budworm, Choristoneura fumiferana (Clemens), egg populations in Maine from 1977 to 1981. Commercially reared California-strain T. minutum were released from the ground at single-point sources in 1977. In 1978, using 4-point-source releases, we found that the native Maine-strain performed better than the California strain. In 1979, broadcast and multiple releases from the ground gave slight improvement in parasitism over 4-point releases. In 1981, three closely timed, aerially broadcast releases from a helicopter yielded increases in parasitism rates significantly higher than those in control plots, but not sufficient to suppress epidemic spruce budworm populations. Important variables and suggestions for future aerial releases are discussed.

A process-oriented model was developed to describe the oviposition of the spruce budworm, Choristoneura fumiferana (Clem.), on an individual and a population basis. The model simulates the effects of temperature on female longevity, oogenesis, and oviposition. The model is structured for ease of incorporation of additional processes such as emigration, immigration, mating, and other behavioral reductions in oviposition activity. Simulation results, at both the individual and the population levels, are compared with laboratory and field data. This model is an element of a model of spruce budworm biology currently under development but, by itself, can be used to study the effects of temperature and dispersal on the fecundity of spruce budworm populations.

Larval densities and catch of adult male Choristoneura fumiferana (Clemens) in pheromone-baited covered funnel traps in the same year were highly correlated. Such traps avoid saturation problems associated with conventional sticky traps. Release of marked males resulted in recapture rates of up to 21% in covered funnel traps. The findings suggest that non-saturating pheromone-baited traps could be used to monitor population densities and trends of the spruce budworm.

Newly moulted sixth instar larvae of spruce budworm, Choristoneura fumiferana, were force fed graded dosages of preparations containing (1) purified crystals, (2) purified spores, and (3) mg/mg mixtures of purified spores and purified crystals. The LD50 for purified crystals was 0.094 μg/larva and for the mixture 0.096 μg/larva but the latter preparation had an LD50 of 0.048 μg/larva based on crystals indicating that the presence of 2.4 × 105 spores enhanced the toxicity of crystals twofold. The LD50 spore crystal corresponded to LD60 for crystals alone. The LD50 for spores treated with proteinase to remove residual crystals was 20 μg/larva, or 1,0 × 108 spores. The regression coefficients were not significantly different from each other in all three preparations indicating a common or similar mode of action. It is concluded that spores play little or no role in mortality of spruce budworm induced by Bacillus thuringiensis insecticides.

Required sample size was determined for early instar (2nd to 4th instar) larvae of spruce budworm, Choristoneura fumiferana (Clem.). Larval counts on mid-crown 45 cm branch tips and whole branches of balsam fir, Abies balsamea (L.) Mill., were described in terms of the negative binomial distribution. The values of common k for the branch tip and whole branch sample units were 1.550 and 1.636, respectively. The required sample size at densities greater than or equal to one appears feasible. It is recommended that the 45 cm branch tip be used to estimate population density of early instar larvae in Newfoundland.

The effect of treatment with juvenile hormone and five of its analogs on embryonic development of the spruce budworm was studied. All compounds were applied topically in acetone solution to budworm egg masses, and all were found to have ovicidal activity. Most active was the dichloro analog, which required a minimum dosage of 50 μg per egg mass to ensure embryonic death in all the treated eggs. A similar result was found for juvenile hormone, while juvabione, ethyl-aromatic terpenoid ether, and farnesyl methyl ether required a dosage of 100 μg per egg mass to achieve this result. At this latter dosage level, 6% of the eggs treated with methyl aromatic terpenoid ether hatched.

Electrophysiological recordings are taken from the antennae of eastern spruce budworm males. These respond to crude pheromone extracts from the females. The pheromone receptors are located along the length of the antennae.

Environmental factors can significantly affect the occurrence of a second diapause in laboratory-reared Choristoneura fumiferana. Each of the following conditions resulted in significantly fewer larvae entering second diapause: incubating the eggs at a high relative humidity (95%); a pre-diapause period at 20 °C rather than 28 °C; a diapause period of 7 or 8 months rather than 4 months; and holding the feeding larvae at higher temperatures (24 °C and 28 °C as opposed to 20 °C). Late-emerging larvae had a greater tendency to enter second diapause.

The morphology and histology of the sex pheromone-producing gland in the females of Choristoneura fumiferana (Clemens), C. pinus (Freeman) (Tortricidae), and Malacosoma disstria (Hubner) (Lasiocampidae) is reported. A review of the literature relevant to such a study is presented in tabular form.

The sex pheromone of the female eastern spruce budworm was identified as trans-11-tetradecenal by a combination of electroantennogram techniques, laboratory bioassays, and chemical analysis. Subsequent field trapping showed that this compound is a potent attractant for both male Choristoneura fumiferana (Clem.) and C. occidentalis Free, thus supporting its identification as a sex pheromone of the eastern spruce budworm and suggesting that it is also a major component in the pheromone system of C. occidentalis.

Two types of sensory hairs on the tarsus of the spruce budworm, Choristoneura fumiferana (Clem.), are described using scanning electron microscopical and histological techniques.