A key, based on morphological characters of adult males, separating six traditionally recognized conifer-feeding Choristoneura species, C. pinus Freeman, C. lambertiana (Busck), C. fumiferana (Clemens), C. occidentalis Freeman, C. biennis Freeman, and C. orae Freeman occurring in Canada and Alaska is provided and illustrated. The newly discovered morphological features, the aedeagus of C. fumiferana and C. pinus with a short apical spine and with many microscopic spicules on the distal half, are used to separate these two species from their western allies C. occidentalis, C. biennis and.C. orae.

Greenhouse trials were conducted to evaluate the effect of treating adult and egg stages of the eastern spruce budworm, Choristoneura fumiferana (Clemens), with Insegar, a water-based commercial formulation of the juvenile hormone analog fenoxycarb, or with water (controls) at droplet sizes and densities comparable to what would be achieved through aerial spraying of field populations. When adult moths were sprayed with the juvenoid at dosages equivalent to 15.5, 155.4, and 310.8 g AI/ha, approximately 90% of the eggs that were subsequently oviposited failed to hatch. The efficacy of the compound (60% suppression of egg hatch) was not as high when the egg stages were sprayed directly at 15.5 and 155.4 g AI/ha. Insegar did not affect the egg productivity of the moths.

The musculature of the pterothorax of the adult male Choristoneura fumiferana (Clem.) is described in detail and the arrangement of muscles is shown to correspond closely to other lepidopterans. A comparison with the general plan of the alate segment is also attempted.

Wasps of the family Ichneumonidae recorded as parasitoids of Choristoneura Lederer (Lepidoptera: Tortricidae) in North America are summarized. A total of 113 species in 45 genera and 11 subfamilies have been reliably reared from 10 species of Nearctic Choristoneura. Twenty-one more species are listed as possible parasitoids of Nearctic Choristoneura, based on rearings from Palearctic Choristoneura species and (or) limited introductions to North America. Well-illustrated identification keys are provided to the subfamilies, all genera, and species of 39 of the genera. The species of Choristoneura used as hosts by the 113 ichneumonid species are tabulated, as well as the wasps’ geographic ranges. The biological characteristics of the ichneumonid subfamilies parasitizing Choristoneura spp. are described and compared. Erroneous Choristoneura host records and synonyms for all ichneumonid taxa previously recorded from Nearctic Choristoneura spp. are given. Phaeogenes gaspesianus Provancher is moved to Dirophanes Förster, forming D. gaspesianus (Provancher) comb. nov. New host records are Phaeogenes cacoeciae Viereck and Scambus hispae (Harris) on C. rosaceana (Harris), D. gaspesianus and Pimpla disparis Viereck on C. fumiferana (Clemens) (P. disparis having been introduced to New Brunswick to control the gypsy moth, Lymantria dispar (L.)), and Exochus turgidus Holmgren on C. occidentalis Freeman.

Male genitalia of Choristoneura species from the Nearctic Region and Palaearctic Region are described and illustrated. The study revealed that the male genitalia are among the most important body parts that contain valuable morphological characters for species distinction or grouping in this genus. They are potentially useful in the clarification of the taxonomic status of species in closely related species groups, such as the spruce budworm species complex in North America.

On the basis of 17 interpretable male genital characters and their corresponding evolutionary states, the phylogeny of the genus Choristoneura is inferred and proposed. Nine species groups are recognized: (1) fumiferana, pinus, biennis, orae, occidentalis, lambertiana, carnana, retiniana, and spaldingiana; (2) diversana, murinana, metasequoiacola, and jezoensis; (3) longicellana; (4) lafauryana; (5) conflictana and fractivittana; (6) hebenstreitella, adumbratana, and luticostana; (7) albaniana and lapponana; (8) rosaceana and parallela; and (9) obsoletana and zapulata.

Morphological evidence obtained in the present study suggests that two conifer-feeding species groups of Choristoneura, species group 1 from the Nearctic Region and species group 2 from the Palaearctic Region, are related. They represent the least evolved species groups in the genus. Choristoneura rosaceana, C. parallela, C. obsoletana, and C. zapulata, representing some of the species feeding on deciduous trees, are among the most evolved Choristoneura species.

We describe an experimental protocol for measuring the response of spruce budworm postdiapause larval development to temperature. This protocol is specifically designed to include measurements of development near their upper and lower thermal thresholds. The application of this protocol to a laboratory colony allowed for the first experimental evidence that spruce budworm larval development occurs at temperatures as low as 5 °C and as high as 35 °C, and it provides data to fit stage-specific development models. Our protocol is also designed to minimise mortality near the thermal development thresholds, thus allowing for multigenerational studies. We observed developmental plasticity in larvae reared at constant temperatures, particularly the occurrence of up to 42% of some individuals requiring only five instars to complete development compared to the expected six instars. The occurrence exhibited no clear relation to temperature. Although this protocol is specifically designed for spruce budworm, it provides a template for the study of other species’ developmental responses to temperature.

Overwintering mortality in the spruce budworm, Choristoneura fumiferana (Clem.), was measured between 1983 and 1990 in several natural stands of balsam fir, Abies balsamea (L.), in Quebec and Ontario. Overwintering losses (disappearance of larvae) averaged 25.2%, occurred mostly in late summer and early fall, and were probably caused by, in large part, failure to spin a hibernaculum, diapause-free development, and invertebrate predation. An average of 24.1% of larvae were found dead in the hibernaculum. This mortality also occurred early in diapause and during post-diapause development, and overwintering mortality did not vary much from year to year. We conclude that overwintering mortality does not result from adverse winter weather conditions or from gradual loss of hibernacula. Overall overwintering mortality from the loss of hibernating larvae plus death within the hibernaculum averaged 43.2% and was not related to infection with the microsporidian Nosema fumiferanae (Thomson). We observed no influence of position in the tree crown on overwintering survival. There was a 40% decrease in overwintering survival among larvae from eggs laid very late in a female’s oviposition sequence. Survival within the hibernaculum on shoots of A. balsamea bearing different types of spinning substrates varied considerably, and was highly correlated with larval spinning preferences. Shoots bearing lichen mats, rough bark, male flower scars, or 1-year-old annular scales were most suitable, whereas shoots bearing annular scales older than 1 year or smooth bark were least suitable. The efficiency of the NaOH extraction technique to recover overwintering spruce budworm larvae was found to be highly variable, and to depend on population density, shoot type, and the proportion of live larvae on the branches.

Because microbial insecticides based on Bacillus thuringiensis subsp. kurstaki cause temporary cessation of larval feeding at sublethal doses, we hypothesized that the delivery of a given dose in a single droplet is more efficacious than delivery of the same dose in multiple smaller droplets. We tested this hypothesis by exposing larvae of the spruce budworm, Choristoneura fumiferana (Clem.), to an LD50 of a commercial product (Dipel 8L) in combinations of droplet sizes and densities that are commonly observed on coniferous foliage after aerial application. A nominal dose of 5.2 International Units (IU) was presented to fifth-instar larvae on one, two, or four balsam fir, Abies balsamea L., needles in the form of one, two, or four droplets with diameters of 84, 66, or 52 μm, respectively. The combinations of droplet size and density were chosen to represent an increasing degree of dose dispersion. Overall mortality after a 24-h exposure was significantly reduced with increasing dose dispersion from an average of 66% when the dose was presented in one 84-μm droplet on one needle to 40% when presented in multiple droplets on several needles. Increased dose dispersion reduced the proportion of larvae that were able to ingest the full dose, presumably because of feeding inhibition caused by ingestion of sublethal droplets. In addition, mortality of fully dosed larvae declined significantly with increasing dispersion, implying a reduction in the effectiveness of the ingested dose. When compared with operational spray deposits, our results suggest that efficacy of spruce budworm sprays may be improved by increasing the proportion of needles receiving a lethal spray deposit by increasing product potency and possibly the active ingredient application rate.

For reasons which will be given in a forthcoming taxonomic paper, the spruce budworm, Archips fumiferana (Clem.), is here transferred to the genus Choristoneura Lederer, 1859, Wien Ent. Monatschr., 3:242. Genotype: Tortrix rusticana Treitschke, designated by Fernald, 1908, The genera of the Tortricidae and their types, p. 53. The transfer is made at present in order that this species may be properly referred to in a following paper dealing with its external anatomy.

The food intake of fourth, fifth, and sixth instar spruce budworm, Choristoneura fumiferana Clemens, was investigated by feeding larvae for 24 h artificial diet incorporating amaranth dye. Amaranth was selected because it followed Beer's law over a wide concentration range, mixed well with the meridic diet, could be extracted in ice-cold water, was not absorbed by larval tissue, had minimal feeding deterrence as well as marginal adverse chronic effects on the larvae, and finally had negligible effect on ingestion rate over a 24 h period. The results indicated that 6th instars consumed 20 times and 5th instars 3 times as much as 4th instars, but when compared on a body weight basis the ingestion rate was similar in all three instars. Temperature and photoperiod influenced the rate of food intake. The application of these findings in assessing defoliation to the forests as well as estimating dosage of pesticides for control of this species are discussed.

The morphology and histology of the internal reproductive system of the female spruce budworm moth, Choristoneura fumiferana (Clemens), is described and discussed, with notes on the spermatophore and egg development.

Predation on spruce-budworm, Choristoneura fumiferana (Clem.), pupae on the forest floor was estimated at 72.5% per day. It is unlikely that many adults of the spruce budworm emerge from the forest floor and there would be little bias introduced in the estimation of apparent fecundity by disregarding pupae on the ground. There were large seasonal fluctuations in the rate of predation attributable to various predator groups; the overall rate ranged from 66 to 91% per day. Low temperatures had no detectable effect on vertebrate predation, but reduced invertebrate predation; however, this effect is unlikely to result in much variation in survival of pupae on the forest floor.

The comparative ecology of conifer-feeding budworms in the genus Choristoneura Lederer (Lepidoptera: Tortricidae) in Canada is reviewed with emphasis on publications since 1980. Systematics and life history are updated and historical outbreak patterns and their current interpretation summarised. Recent evidence is analysed in the context of ecological interactions among three trophic levels; host plant, budworm herbivore, and natural enemies. The influence of weather and climate are viewed as modulating factors. The population behaviour of budworms is interpreted as the result of tri-trophic interactions that vary at different scales. The result of these multi-scale interactions is that despite shared phylogenetic constraints and common adaptations, different budworm species display different population behaviour because of specific ecological relationships with their respective hosts and natural enemies.

Section 7 of the primary simplex of the ductus ejaculatorius of unmated male spruce bud worm moths, Choristoneura fumiferana, contains a yellow substance that is not present in recently mated males. The yellow substance occurs in laboratory-colony males reared on diet and in feral males reared on foliage. It is shown that the presence/absence of this material is a reliable index of copulation during the previous 24 h. Although the yellow substance regenerates over a period of several days, males 0–72 h post-copulation may be indexed when compared with unmated males of similar age.

Four commercial sex attractant traps were evaluated for monitoring low density spruce budworm (Choristoneura fumiferana (Clem.)) populations. Factors considered were color, the number of male budworm caught, durability of traps and their ability to exclude non-target insects and debris. The Pherocon 1CP was superior to 3-M Brand Sectar 1 and XC-26; Pherocon 1C was least suitable. Interpretation of the numbers captured may be confounded by the fact that trapped males repel other males.

This paper deals with the orientation reactions exhibited by larvae and adults of the spruce budworm, Choristoneura fumiferana (Clemens), (12) in response to stimulation by light. The insect is an important pest of the coniferous trees, Abies balsamea Mill, and Picea spp., which compromise the pulpwood stands of the forests of northeastern North America. Hence, at present, it is the subject of many investigations. The work reported here is part of an investigation designed to provide data for the development of studies of the effects of weather and climate upon the spruce budworm.

Male spruce budworm moths were kept in a wind tunnel for 4 days and assayed each day to determine their ability to locate calling females that were surrounded by rubber septa loaded with synthetic pheromone, a 95:5 blend of E:Z-11-tetradecenal. As the concentration of synthetic pheromone increased, the numbers of males successfully locating females decreased, the latency of response increased, and the speed of flight decreased. At release rates from the septa close to those of a calling female, 6–60 ng/h per septum, most disrupted males flew to a septum instead of the females. At the highest release rate tested, 600 ng/h, many males were inactive or flew to the sides of the tunnel, which indicates sensory fatigue. This effect was more pronounced among males that were continuously exposed to the synthetic pheromone for the 4 days than among males kept in pheromone-free air between assays. About a quarter of the males died or became unable to fly after the 4 days, but there was no change in the proportions of the different responses of males, or in their response times, with increasing age, nor was there evidence that males were conditioned by their experience on previous days. The results led to the conclusion that time-averaged atmospheric concentrations of the synthetic pheromone as high as 20 ng/m3 are necessary to achieve effective disruption of the orientation of male spruce budworm moths to calling female moths.

The spruce budworm, Choristoneura fumiferana (Clemens), was reared on a synthetic diet. Comparison of two successive laboratory generations reared on synthetic diet and on frozen balsam fir buds showed that diet-fed insects had a higher survival, developed faster, were heavier, mated more successfully, and were more fecund.

Fifth-instar larval mortality was compared between male and female Choristoneura occidentalis Freeman exposed in the laboratory to sublethal doses of Choristoneura fumiferana (Clem.) multicapsid nuclear polyhedrosis virus (CfMNPV) with or without optical brighteners. More females than males died when the virus was used alone, but differences were not significant. When 1% brightener was added to CfMNPV suspension, differences in larval mortality between males and females were significant for three of the four brighteners tested. In addition, times at which 50% of the larvae died indicated that female larvae died 23 and 39% more quickly than male larvae, respectively, when brightener Blankophor HRS and Tinopal LPW were added to the virus, whereas at times at which 95% of the larvae died indicated that females died 33 and 54% faster than males. Alteration of sex ratio favoring male survival can play a significant role in the biological control of C. occidentalis by the virus.

Experiments were conducted using balsam fir twigs treated with Bacillus thuringiensis Berliner to examine the influence of temperature and exposure time on mortality of spruce budworm, Choristoneura fumiferana Clemens. Twigs were sprayed with a commercial formulation (8.4 BIU/L) using droplets of 40–70 μm diameter at densities, ranging from 0.5 to 5.5 droplets per needle. Temperature affected progression but not the level of cumulative mortality during 14 days of feeding on sprayed foliage. The LT50 decreased from 12–17 days at 13°C to 2–4 days at 25°C, depending on droplet density. Temperature between 13 and 25°C had a limited effect on dose acquisition because 40–60% of the larvae were able to acquire a lethal dose within 1 day of feeding on foliage with 0.5–1.5 droplets per needle, regardless of temperature. Under these conditions dose acquisition was not limited by temperature-dependent consumption of foliage, but rather by feeding inhibition associated with the dose initially ingested. This also limited the influence of exposure time; a 7- or 14-fold increase in exposure time increased larval mortality at most by 25%. Implications of these findings for improving efficacy of B. thuringiensis in forestry applications are discussed.