A previously undescribed entomopoxvirus was isolated from larvae of Choristoneura conflictana Wlk. Samples of larvae taken from several points in Ontario indicated that the virus was widespread in the Province.

The morphology of the virus is described. The inclusion bodies are larger than those of another entomopoxvirus originally isolated from Choristoneura biennis Free. and propogated in Choristoneura fumiferana (Clem.). The virions are of the same order of size for both viruses. Microspindles are associated with these viruses and some of the spindles are occluded along with the virions within the oval inclusion bodies. The C. conflictana entomopoxvirus is also infectious to C. fumiferana.

Parasitism by Apanteles and Glypta spp. on spruce budworm in five localities in Quebec in 1975 was exceptionally high, averaging 52%. The frequency distribution of attacks of these species, and the outcome of inter- and intraspecific progeny competition are described, using dissection data. Superparasitism occurred on a Poisson distribution, but rates of multiparasitism lower than expected indicate interference between Apanteles and Glypta spp.

Factors influencing spruce budworm (Choristoneura fumiferana) mating and mating suppression in an enclosed environment in the laboratory were investigated to develop a quantitative assay suited to statistical analysis. Mating in the absence of the two major components of spruce budworm sex pheromone (control) was not affected by changes in moth population density nor by increasing the experimental duration from 20 to 44 h. The proportions mated increased with an increase in the male:female ratio to 1.5:1 and when the experimental duration was prolonged to 68 h. Using a population density, sex ratio combination of 15:10 (male:female) the proportions of mated females decreased with increasing source concentrations of the two major spruce budworm sex pheromone components (95:5 E/Z-11–14-tetradecenal). This effect was diminished with increases in the population density and with extended test duration. Mating in the presence of pheromone remained lower than controls over all durations tested.

An electroantennogram (EAG) technique, which indicates electrochemical activity in a whole antenna, was used to study sex pheromone reception in spruce budworm moth antennae. For both males and females the EAG exhibited a phasic depolarization, reaching maximum near the end of a puff stimulation, followed immediately by repolarization which was prolonged by increasing amounts as the source concentration of the pheromone was increased. The dose–response curves for both sexes were sigmoid in shape, but they indicated that female antennae have a higher threshold and a lower peak response than that of males. Antennal response changed with age, being a regular increase and decrease for females and irregular for males.

I review reports on the genetic basis for species differences in the Lepidoptera. In the six best-studied species complexes, more than half of all ecological, behavioral, or physiological differences among species are controlled by X-linked genes. Because Lepidoptera have about 30 pairs of chromosomes, this finding clearly indicates strong bias toward X-linkage of genes for species differences. The proportion of X-linked species differences ranges from complete X-linkage in Colias butterflies, to almost none in Yponomeuta moths. Four other complexes all have at least one X-linked gene that is crucial to species differences, including the Choristoneura fumiferana Clemens, Papilio glaucus L., and Papilio machaon L. species groups, and Ostrinia nubilalis Hübner pheromone strains. The mechanisms that account for this phenomenon are open to speculation. Nonetheless, an interesting implication of disproportionate X-linkage is that reproductive isolation may frequently arise by selection on linkage complexes, rather than as a random byproduct of evolution in geographically isolated populations. If confirmed, the bias toward X-linked species differences may also help efforts to find characters that distinguish host races and sibling species, as well as provide an avenue by which genes crucial to speciation can be more easily mapped and characterized at the molecular level.

During 1972, spruce budworm infested white spruce and balsam fir trees were sprayed aerially with a low dose of fenitrothion (0.25 oz AI/ac), entomopox virus (EPV) at 7.6 × 1010 polyhedra/ac, nuclear polyhedrosis virus (NPV) at 2.7 × 1011 polyhedra/ac, or each virus–fenitrothion combination. Fenitrothion (active ingredient), NPV, and EPV deposited at ground level at 5%, 31%, and 42%, respectively, of the amounts emitted.

In the year of application, NPV + fenitrothion was highly effective in population reduction and foliage protection especially on; balsam fir although a higher virus infection rate was found on white spruce than on balsam fir. EPV + fenitrothion also provided a high level of foliage protection and apparently reduced surviving female:male sex ratio to 1:2 compared with the normal 1:1 ratio. NPV + insecticide caused highest larval mortality, highest incidence of virus, lowest rate of moth emergence, fewest progeny, and lowest rate of progeny survival. The natural incidence of microsporidia was low in all plots.

In the year following application, the NPV + insecticide treated plot again showed lowest population density, highest larval mortality and incidence of virus, and low defoliation and egg mass density. However, there was a higher proportion of viable eggs deposited than in the previous year. Egg parasitism by Trichogramma minutum increased by 1.5 to 4.2% in plots treated with virus only and declined by 1.6 to 10.5% in insecticide treated plots and by 1.2% in untreated check plot. The transmission of the virus from one year to the next is considered to be of paramount importance in the future use of this pathogen in spruce budworm control.

Male moths of Choristoneura occidentalis Freeman, C. biennis Freeman, C. fumiferana (Clemens), and C. orae Freeman were caught in pheromone-baited traps. Ten traps were placed at each site, five baited with an aldehyde lure and five with an acetate lure. This procedure permitted separation of species based on the specific chemical lure and also provided specimens for further study of morphological and isozyme differences. The color of the forewings, presence or absence of spicules on the aedeagus, and a specific allozyme frequency were determined on selected specimens where these characteristics were useful in separating species at a particular site. Distributions of all species were more extensive than previously known, sometimes adding hundreds of kilometres to the recorded range. Areas of sympatry were identified and the fidelity and usefulness of characteristics for separating species in areas of overlap were discussed.

Fifty Bacillus thuringiensis (B.t.) isolates representing K-1, galleriae, K-73, thuringiensis, aizawai, dendrolimus, tolworthi, kenyae, darmstadiensis, alesti, and entomocidus crystal antigen types were bioassayed against fifth-instar spruce budworm, Choristoneura fumiferana (Clem.), larvae. In addition, larvae reared on diet with and without aureomycin were tested for their susceptibility to B.t. The data indicated no significant differences in susceptibility to B.t. among insects reared on aureomycin or on aureomycin-free diet, but differences were evident in larval growth and mortality among untreated controls. None of the 50 isolates bioassayed was any more toxic to the budworm than is the strain used at present in commercial preparations of B. thuringiensis.

The posterior apophyses in terminal abdominal segments of female moths form part of the sex pheromone gland in each of three species examined (Choristoneura fumiferana (Clem.) (Tortricidae), Trichoplusia ni (Hübner) (Noctuidae), Orgyia leucosligma (J.E. Smith) (Lymantriidae)). Four groups of paired dorsolateral muscles are attached to the anterior or posterior apophysis and the integument. An additional group is attached to the anterior and posterior apophyses. The probable relationship of these muscles to the eversion, or protrusion, and inversion of sex pheromone glands is discussed.

Male spruce budworm moths, Choristoneura fumiferana (Clem.), were captured in 1986 and 1987 and the proportion recently mated was determined for each sample. Mating status was examined in relation to trap location, sampling method, sampling date, and adult emergence. On a given day the proportion of recently mated males captured was similar among pheromone-baited traps both within and among test sites. The number of males trapped increased with increasing trap elevation, although there was no difference in the proportion of mated males at each elevation. Males exhibiting “mate-location behaviour” were captured individually with an insect net and were found to be mated in the same proportion as those caught in pheromone-baited traps. The proportion of recently mated males trapped tended to increase during the early part of the flight season, to fluctuate during the middle portion, and then to decline toward the end of the season. This pattern was due, in part, to adult emergence trends.

Predators of the spruce budworm, Choristoneura fumijerana (Clem.), include both invertebrates and vertebrates (Jennings and Crawford 1985). Birds are the best known and most extensively studied vertebrate predators, but because of their arboreal and omnivorous feeding habits, the deer mouse, Peromyscus maniculatus (Bangs), and the red squirrel, Tamiasciurus hudsonicus (Bangs), often are implicated as potential predators of budworm larvae and pupae (Morris et al. 1958; Morris 1963; Otvos 1981; Welsh 1983). In laboratory feeding trials, W.F. Chesire estimated that red squirrels had a mean food capacity of 600–700 mature larvae or pupae of the spruce budworm per day (Morris 1963). R.T. Mitchell examined the stomach contents of 25 red squirrels collected during a major spruce budworm outbreak in northern Maine (Dowden et al. 1953); he found that spruce budworms made up 51% of their total food. On the basis of these results, Dowden et al. (1953) estimated that a red squirrel could eat 400–500 larvae per day.

The spruce budworm, Choristoneura fumiferana (Clem.), has an obligatory winter dormancy period that lasts up to 10 months in the field. In the Great Lakes Forestry Centre rearing facility, neonate larvae spin hibernacula in cheesecloth, which is then stored at 2 °C for between 20 and 30 weeks. Although dormancy survival and synchrony of postemergence development are highest when larvae are stored in the cold for 16–35 weeks, it is not known how cold-storage duration affects spruce budworm performance once diapause has been completed. We exposed approximately 9250 second-instar larvae (belonging to three rearing cohorts) to 2 °C for 16, 19, 22, 25, 28, 31, 34, or 37 weeks and monitored various postdiapause performance variables. Increasing cold storage from 16 to 25 weeks or more resulted in small (approximately 10%) increases in dormancy survival and larval development rates (from second instar to pupation), a larger (up to 23%) increase in pupal mass and realized fecundity (number of eggs laid per female), and an increase of at least 25% in late-instar survival (from fifth instar to pupation). The only variable that was negatively affected was the pupal survival, but the decrease was relatively small. Therefore, storing diapausing larvae for at least 25 weeks optimizes postdiapause performance variables that are important for mass-rearing efficiency.

This is the second of a series of papers (Miller, 1959) describing the interaction of primary parasites and the spruce budworm, Choristoneura fumiferana (Clem.), based on data collected during an outbreak of the budworm in northern New Brunswick during the period 1947–1958. The first paper showed that the interaction between the spruce budworm and Apanteles fumiferanae Vier. is adequately described by the general mathematicai model developed by Watt (1959). The data on the parasite Glypta fumiferanae (Vier.) to be presented in this paper are also analysed by means of Watt's model and consequently the method is essentially the same. There is, however, one important difference. In the case of A. fumiferanae, the estimated number of adult parasites was only an index based on the potential number emerging from the previous host generation. The observed density of G. fumiferanae is a more realistic estimate. It is based on the actual number of cocoons found on the foliage during the adult emergence period.

In laboratory tests on the spruce budworm, Choristoneura fumiferana (Clemens), EL-494®, a new moult-inhibiting insect growth regulator, was found to be more active than Dimilin. The EC50 determined by diet tests was 0.205 ppm for the 3rd, 0.249 for the 4th, 0.287 for the 5th, and 0.486 for the 6th instars. Stadial sensitivity was not detected.

In greenhouse tests this compound was found to be resistant to leaching and UV-degradation; the compound remained active on spruce foliage for at least 15 days. In preliminary field tests EL-494 showed good potential as a control agent.

The genetic make-up of representative populations of five Choristoneura species was compared using starch gel electrophoresis. Species included C. occidentalis Freeman from Idaho, C. biennis Freeman from British Columbia, C. retiniana (Walsingham) (= C. viridis Freeman) from Oregon, C. lambertiana ponderosana Obraztsov from Colorado, and C. fumiferana (Clemens) from Maine. When variation at individual gene loci was examined, intraspecific variation was often as great, and sometimes greater, than interspecific variation and few significant differences were noted among the species. The highest levels of overall genetic similarity occurred among C. occidentalis, C. biennis, and C. retiniana. Relatively greater genetic distances were found between this group and C. lambertiana and C. fumiferana. C. fumiferana was most distantly related to all other groups. Genetic identity values fell within the range more commonly associated with conspecific populations rather than with separate species.

The last larval stadium of the spruce budworm, Choristoneura fumiferana (Clemens), is extended, if infection by an entomopoxvirus is in an advanced stage at the normal time of pupation. The larvae attain an abnormally large size. Part of this increase in size is caused by a proliferation and subsequent infection and swelling of fat body cells.

The spruce budworm, Choristoneura fumiferana (Clemens), is susceptible to two types of granulosis virus. One is characterized by the formation of mostly small ellipsoidal inclusion bodies, the second by the formation of large cubic inclusion bodies. Different shapes and sizes of inclusion bodies were formed when these viruses multiplied in the same tissues, some resembling the ellipsoids, others the cubes.

Ingestion of 0.1 μg of RH-5992, tebufenozide, by early 6th instar larvae of the spruce budworm, Choristoneura fumiferana (Clem.), prior to the appearance of the ecdysone peak in the hemolymph, resulted in the induction of a precocious incomplete moult that was lethal. The larvae stopped feeding within 8 h post ingestion and remained quiescent just as they do in preparation for a normal moult. Head capsule slippage started at 12 h post ingestion, became pronounced by 24 h, and by 48 h an untanned new head capsule was visible behind the old one. The lack of tanning of the new cuticle was due to the failure of dopadecarboxylase gene expression. Although the old cuticle was loose around the entire body, indicating that apolysis had occurred, there was no evidence of ecdysis of the old cuticle, suggesting that eclosion hormone was probably not released. Earlier instars required a lower dose than the later ones to elicit an "all or none" type of moulting response. The most effective routes of entry were by intrahemocoelic injection, followed by ingestion. Topical application was effective only when nonaqueous carriers such as acetone or dimethyl sulfoxide were used. The larvae were unable to discriminate between treated and untreated diet over a 48-h period. The transcription factor, Choristoneura hormone receptor 3, which is normally expressed at the onset of the hemolymph ecdysone peak, was expressed in the epidermis 1 h post ingestion of RH-5992, reached a peak level by 3 h, and became undetectable by 24 h, confirming that this analogue acts through the ecdysone receptor system. Greenhouse tests using potted white spruce trees sprayed with RH-5992 and colonized with 4th-instar spruce budworm indicated that field dosages of 35, 70, 140, and 280 g/ha would all be effective. Ground spray trials conducted in a spruce budworm infested white spruce stand in Zee Casault, Gaspé, Quebec, using a backpack sprayer showed that ≥ 70 g/ha of RH-5992 reduced the insect population by 100% with very little defoliation and was better than Chlorfluazuron® (an analogue of the chitin synthesis inhibitor, diflubenzuron or Dimilin®) treatment, which was used as a positive control. The unique mode of action of this ecdysone agonist and its effectiveness as an environmentally benign control agent for the spruce budworm are discussed.

During the summer of 1982, aerial experimental sprayings were carried out with a new formula of Bacillus thuringiensis named Futura®. This formula provided a treatment of the 20 × 109 IU of B. thuringiensis/ha required for suppression of spruce budworm (Choristoneura fumiferana), in a final volume of 2.5 L/ha. Results of spraying with Grumman AgCat and DC-4G aircraft are presented. These results were compared with those obtained with formulas of B. thuringiensis used in the past at 4.7 L/ha. Futura® caused 91.1 and 88.7% larval mortality and resulted in 86.6 and 75.1% foliage protection with the Grumman AgCat and DC-4G aircraft, respectively. Such results were equal to or better than those obtained with the formulas used earlier at 4.7 L/ha and confirm the feasibility of using B. thuringiensis operationally in an efficient and economical way.