Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae) multiple nucleopolyhedrovirus (CfMNPV) expressing green fluorescent protein was used to study aspects of nucleopolyhedrovirus infection in the spruce budworm. The temporal and spatial distribution of fluorescence indicated that the virus infected the midgut, entered the tracheal system, and traveled to the epidermis, fat body, and muscles. In contrast to Autographa californica (Speyer) (Lepidoptera: Noctuidae) multiple nucleopolyhedrovirus (AcMNPV) infection, hemocytes from infected C. fumiferana did not exhibit fluorescence until after CfMNPV had passed from the midgut into the tracheae. Therefore the role of hemocytes may be limited during CfMNPV infection. Also the fluorescence pattern spread from the tracheolar cells to tracheal epithelial cells throughout the tracheal system. Our results indicate that the temporal and spatial events involved in CfMNPV infection of C. fumiferana larvae are consistent with those observed in other lepidopteran hosts infected with AcMNPV Minor deviations between these two systems may be attributed to differences in virulence, infection rate, and possibly host range of the virus.

Breeding experiments and rearing under variable controlled conditions have revealed that western and 2-year-cycle spruce budworms (Choristoneura occidentalis Freeman and C. biennis Freeman, respectively) from British Columbia, Canada, and their hybrid progeny have the inherent capacity for a variable number of diapause events and hence voltinism. While all crosses have at least one diapause, variability in the relative frequency of a second diapause is determined by genetic traits modified by the photoperiod and, to a lesser extent, temperature experienced during the larval stages. Second diapause appears fixed in C. biennis but is facultative and most frequent at short photophases (12L:12D) in C. occidentalis. Hybrids and backcrosses had responses intermediate to the parental responses under all environmental conditions. The occurrence of a facultative third diapause in all crosses underlines the inherent capacity for flexibility in voltinism in these species. These results are discussed in the context of past, present, and future distributions of alternative life cycles in closely related species.

Interactions between Bacillus thuringiensis Berliner and Apanteles fumiferanae Viereck as mortality factors of the spruce budworm, Choristoneura fumiferana (Clemens), were investigated by placing parasitized and nonparasitized budworm larvae on foliage with and without spray deposits of a commercial formulation of B. thuringiensis. The effect of larval age (and, thus, the timing of spray applications) was examined by using peak third-instar and peak fourth-instar larvae. We demonstrated that parasitized larvae are more likely to survive exposure to B. thuringiensis because they feed less than non-parasitized larvae and are thus less likely to acquire a lethal dose of the bacterium. Bacillus thuringiensis nevertheless reduced parasitoid populations by 50–60% by killing their hosts before parasitoid emergence. This negative impact of B. thuringiensis on parasitoid survival was decreased when exposure of budworm larvae to spray deposits was delayed from peak third to peak fourth instar. The enhanced survival of parasitoids offset the lower mortality as a result of B. thuringiensis in the delayed sprays. We conclude that B. thuringiensis applied when budworm larval populations are at peak fourth instar or later would complement rather than interfere with the beneficial effects of A. fumiferanae. The implications for budworm management strategies are discussed.

Field data from outbreaks of the spruce budworm, Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae), in Ontario and Quebec show that current-year defoliation is the single greatest determinant of variation in fecundity. The species of tree that served as the foodplant and infections by the microsporidian Nosema fumiferanae (Thomson) (Microsporida) had little effect on mean lifetime fecundity in field populations. During a prolonged outbreak at one location (Black Sturgeon Lake, Ontario), annual lifetime fecundity was inversely related to observed defoliation in the same year, with the highest mean fecundity recorded at the beginning and the end of the outbreak when defoliation was least severe. The overall trend in yearly rate of change in egg density in a population time series at Black Sturgeon Lake was associated more closely with generational survival than with fecundity. Measured fecundity of local moths was greater than estimated per capita rates of recruitment in most years of the outbreak at Black Sturgeon Lake. This suggests that in these years of the outbreak at Black Sturgeon Lake there was a net emigration of egg-carrying moths.

Either (E)- or (Z)-11-tetradecenal, the two pheromone components, or one analogue, 9-(cyclopent-2-en-1-yl)-nonanal, effectively reduced mating of spruce budworm moths, Choristoneura fumiferana (Clem.), in the laboratory. The results suggest that different behavioural and physiological processes may be occurring in pheromonal attraction and close range mating prevention in the spruce budworm.

A 4000-ha block of spruce budworm, Choristoneura fumiferana (Clem.), infested forest in western New Brunswick was sprayed repeatedly in 1975 during the larval stage of budworm development. The objective was to reduce the population of the 1975 generation to a minimum level so that most of the following generation eggs found on the block could be attributed to invading females, thus providing data on the impact of moth invasion.

The presence of dispersing adults in the airspace over the block was monitored by a ground-based radar unit while light traps and pheromone-baited traps were used to confirm that invasion had taken place. A total egg population of 33.8 masses per m2 of foliage was found on the block and indirect estimates suggest that invading females deposited about 10 of these masses.

The efficiency of two sticky-bottomed traps and seven high-capacity, nonsticky traps in catching male spruce budworm [Choristoneura fumiferana (Clem.)] moths was evaluated in a wind tunnel. The place where the male moths first contacted the trap, the length of time that passed until they entered the trap, and the number remaining in the trap after 5 min were recorded. The most efficient traps were the Pherocon 1 C, a sticky-bottomed trap, and the Multi-Pher and Uni-trap, both nonsticky traps with internal funnel-shaped baffles that prevent moths from escaping. As sticky traps become saturated at relatively low densities they are not suitable for monitoring wide changes in population density. The Multi-Pher and Uni-trap are therefore recommended for monitoring population changes of the spruce budworm, establishing thresholds for management action, and estimating population density.

The musculature of the prothorax and the prothoracic coxa of the adult male Choristoneura fumiferana (Clem.) is described in detail and is compared with three other families of the Lepidoptera.

Exploratory data analysis was employed to investigate the regional dynamics of managed budworm populations based upon survey data reporting spruce budworm egg-mass densities and damage to balsam fir. The Maine Forest Service collected these data annually from 1975 to 1980 at approximately 1000 different locations each year throughout Maine's spruce–fir forest regions. Although spraying was often associated with ‘better’ conditions in heavily defoliated or infested areas, it was generally associated with somewhat ‘poorer’ conditions in areas which had experienced only light defoliation or infestation in the previous year. The analysis also indicated that while insecticide application may reduce budworm larval populations immediately after application, the largest relative decrease in defoliation rates appeared the year after insecticide application. Insecticide treatments were not as effective as expected. In the year following application, the maximum reduction observed in average defoliation was 20% and in average egg-mass density the maximum reduction was 50%. In many cases the reduction was substantially less. Spraying was not associated with any substantial decline in hazard rating.

Neem seed extract (20, 60, and 180 ppm azadirachtin) applied to the crowns of black spruce trees immediately prior to female reproductive bud flush, resulted in high mortality of early instar spruce budworm larvae. Dose-dependent reductions of 40–93%, as compared with check trees, were observed 2 and 4.5 weeks after treatment. Seed cone protection from grazing damage, however, was moderate; at 60 ppm azadirachtin, the incidence of cone grazing was reduced 29%, and the proportion of severely grazed cones reduced 39%, as compared with check trees. Larval mortality and bud damage observed in the laboratory corroborated field results. High toxicity to second-instar larvae, and performance during adverse weather conditions, supports the potential of neem seed extract for control of spruce budworm defoliation. However, both laboratory and field results indicate that feeding occurs before the effects of neem seed extract manifest, resulting in moderate protection of cones. Whereas foliage can tolerate low levels of feeding, female strobili are damaged significantly. Excellent protection of foliage was achieved from systemic injections of neem seed extract to white and black spruce trees (1.5 g azadirachtin/tree). Neem seed extract, formulated for systemic application, could provide a botanical alternative for control of forest pests in urban environments.

Tebufenozide (Mimic) kills Lepidoptera larvae that ingest it. Aerial applications of tebufenozide were made against spruce budworm (Choristoneura fumiferana (Clemens)) (Lepidoptera: Tortricidae) in boreal forest in Manitoba, Canada, in 1999 and 2000. In 2000 and 2001, moths in sprayed and unsprayed plots were sampled with light traps; trapping was supplemented by foliage sampling. Relative to unsprayed plots, catches of spruce budworm moths in plots sprayed in 1999 and 2000 were depressed in 2000, but not in 2001. Host tree defoliation was reduced in 2000 by 1999 and 2000 applications; the 2000 application reduced numbers of spruce budworm larvae in 2000 and 2001. Multivariate analysis revealed negative effects of tebufenozide application on two species of non-target moths in 2000 and no negative effects in 2001. Negatively affected species have larvae feeding in the tree canopy at the time of spray application. Higher catches of non-target species in sprayed treatments were observed for three species in 2000 and two species in 2001. We conclude that tebufenozide can depress the numbers of spruce budworm larvae and provide foliage protection during the year of application and the following year, and that negative effects on non-target species are detectable for about 15 months after application.

Multiyear benefits or carryover effects of single treatments of Bacillus thuringiensis (B.t.) have been suggested in a few reports. Morris (1977) noted that over 2 to 3 years after treatment both defoliation by and oviposition rates of the spruce budworm (Choristoneura fumiferana) were lower in B.t.-treated plots than in untreated plots. Smirnoff et al. (1974) suggested that “metabolic perturbations” in survivors of B.t. treatments affected fecundity and numbers the following year. With other insects, Ruelle et al. (1977) suggested multigenerational effects in the browntail moth, Euproctis chrysorrhoea, and Pruett et al. (1980) described an “exceptional” case with the Siberian silkworm, Dendrolimus sibericus, where over-wintering larvae harbored sublethal infections of B.t., which spread to subsequent generations.

We examined the cocoons of six species of the genera Apanteles and Dolichogenidea attacking spruce budworm, Choristoneura fumiferana Clemens, and Microlepidoptera in the same microhabitat in an effort to overcome taxonomic and ecological problems associated with the identification of these species when adults fail to emerge from their cocoons. Neither cocoon length nor width nor ratio of length to width could be used to identify the six species, owing to considerable overlap in these attributes among the species and the effects of the source of the cocoons. Using a simple technique to examine webbing characteristics of the cocoons, however, we found that each species has a unique banding pattern, determined by the manner in which the density of the webbing varies along the length of the cocoon. This pattern can be used to reliably identify each species. We describe and illustrate the webbing characteristics of each species and provide an identification key based on these characteristics.

Three body dimensions (body length, head width, and abdomen width) were used to determine size differences between laboratory-reared and wild populations of Trichogramma minutum Riley. Six separate groups of T. minutum were measured: three groups were from Sitotroga cerealella (Olivier) eggs, two from spruce budworm Choristoneura fumiferana (Clemens) eggs, and one from wild populations of spruce budworm.

Female T. minutum from spruce budworm (large host) eggs were significantly larger for all body dimensions than T. minutum from S. cerealella (small host) eggs. Male T. minutum from field-collected spruce budworm eggs were significantly larger for all body dimensions than T. minutum reared for more than one generation in S. cerealella eggs.

A significant reduction in female parasitoid size was observed during the initial generations of T. minutum reared in the smaller host (S. cerealella). However, this size reduction was not permanent. Following numerous generations in the S. cerealella host eggs, a significant increase in female parasitoid size was noted within the first generation of T. minutum reared in the spruce budworm host eggs.

Amylopectin added to a sugar-free wheat-germ diet was equal to or better than sucrose as a carbohydrate source, and appears to be readily utilized by the eastern spruce budworm (Choristoneura fumiferana (Clem.)). Larval growth on diets containing dextrins or potato starch shows that they are partly utilized. Starches from other sources, including those isolated from mature balsam fir (Abies balsamea (L.) Mill.) or white spruce (Picea glauca (Moench) Voss) needles, are not utilized to any extent, on the basis of larval growth on diets to which they have been added.

Sixth-instar budworm reared on artificial diets contain amylase(s) in midgut and salivary gland homogenates, which show a low rate of digestion of starches from host foliage. However, the presence of appreciable starch in frass from foliage-fed insects and the apparent low utilizability of foliar starch indicate that the latter is not an important nutrient for the budworm under natural conditions.

Relationships between temperature and development rates of eggs, overwintered second-instar larvae, and all larval stages of Choristoneura fumiferana (Clem.) fed on artificial diet were determined. Egg development was observed at eight constant temperatures between 7 and 32°C. It was fastest at 30°C, and showed relatively little variability. The rate of emergence of overwintered second-instar larvae was observed at 10 constant temperatures between 4 and 33°C. Maximum development rates occurred at 30°C. Variability in emergence rates was large, but unimodal. Development rates of the second to sixth larval instars were measured at 10 constant temperatures between 7 and 36°C, and maximum rates were observed, again, at 30°C. Variability in the development rates of the larvae was large, with no correlations between the development rates of the various larval instars. The results of computer simulations of the insect’s seasonal history are presented and discussed.

The spruce budworm Choristoneura fumiferana (Clem.) is the most damaging insect of the balsam fir Abies balsema (L.) Mill. (Pinaceae) and the white spruce Picea glauca (Moench) Voss (Pinaceae) throughout eastern North America. In outbreak conditions, close to 100% tree mortality can occur in untreated mature fir stands (MacLean 1980). Bacillus thuringiensis var. kurstaki (Bacillaceae) is currently used to reduce spruce budworm damage (Van Frankenhuyzen and Payne 1993). Other possible biological control agents, such as baculoviruses, are also investigated to complement the use of B. thuringiensis. Baculoviruses are advantageous because they occur naturally in several insect species and are generally host specific (Federici 1993).

A systemic tree injection tube was designed to introduce the required volumes of neem-based bioinsecticides into conifer trees. The device consists of plastic tubing attached with hose clamps to a maple sap spile at one end and a tubeless automobile tire valve at the other end. A hole is drilled in the tree, the spile is hammered into the hole, the device is filled with the systemic insecticide, and the system is pressurized by attaching a bicycle pump to the tire valve. The parts are readily available, the device is simple to construct and easy and quick to install on a tree, application volumes are adjustable, and the device is reusable. This device has been used successfully to inject 188 trees representing four conifer species in either spring or fall, primarily with neem formulations but also with dimethoate, imidacloprid, and acephate. In most cases, all of the material was injected into the trees without leakage, although neem formulations were characteristically slow to enter the trees and certain neem formulations were not injected completely at volumes above 15 mL per injection tube. Dosages of 0.2 g azadirachtin/cm of diameter at breast height (dbh) or less provided control of pine false webworm, spruce budworm, cedar leafminers, gypsy moth, and introduced pine sawfly on red pine, white spruce, eastern white cedar, white pine, and white pine, respectively. Dosages as low as 0.005 g active ingredient/cm of dbh applied with injection tubes in either one or two holes per tree resulted in a 95% reduction in defoliation of mature (mean dbh ± SD = 23.4 ± 3.3 cm) red pine caused by pine false webworm.

The braconid parasitoid Meteorus trachynotus Vier. was found in overwintered larvae of the obliquebanded leafroller, Choristoneura rosaceana (Harr.), on foliage of a variety of deciduous species, well before the parasitoid’s attack on the spruce budworm, Choristoneura fumiferana (Clem.). In the spring, percentage parasitism of C. rosaceana by M. trachynotus was 8.0 and 18.8% in 1986 and 1987, respectively. Maximum parasitism on C. fumiferana (35 and 4% in 1986 and 1987, respectively) was reached in late June, at a time when over 50% of M. trachynotus cocoons found on deciduous vegetation had emerged. Twenty days later, parasitoids produced on C. fumiferana reached 50% adult emergence. The catches of adult parasitoids on sticky traps placed on deciduous trees and on conifers showed two periods of adult activity. Based on the sex ratio of captured parasitoids, male M. trachynotus were active at emergence sites, whereas females were found mostly in the habitats of available hosts. The phenology of C. rosaceana was observed in 1987. As indicated by light-trap captures, males fly sooner than females. Eggs were laid in July, and so the early larval stages were available to female M. trachynotus as overwintering hosts. Several parasitoids common to C. rosaceana and C. fumiferana were identified.