In the boreal forest of northwestern Ontario, where carpenter ants (Camponotus spp.) construct extensive underground tunnels, few worker ants were seen on the aerial portions of trees containing colonies of the ants or on neighboring trees, even though the trees were infested by large numbers of spruce budworm [Choristoneura fumiferana (Clem.)] larvae. Immunochemical techniques detected less spruce budworm soluble protein in worker ants from this area than in a laboratory colony that had been fed budworm larvae, or in a colony located in a spruce tree that was surrounded by gravel where the ants were unable to build underground tunnels and instead foraged extensively in the tree crown. This suggests that, in contrast to evidence from western North America, carpenter ants in the boreal forests of northwestern Ontario, and perhaps elsewhere throughout the range of the spruce budworm, are of limited importance as predators of the spruce budworm.

During a severe outbreak of spruce budworm, Choristoneura fumiferana (Clem.), some balsam fir trees, Abies balsamea (L.) Mill., remain noticeably greener than others in the same stand. We show that this ‘green’ tree phenomenon is not caused by differential defoliation in which certain trees experience consistently low defoliation pressure throughout an outbreak. Rather, these trees remain ‘green’ because of their prolific, epicormic shoot production which is consistently high during an outbreak, giving them a ‘greener’ appearance than other trees that produce lower numbers of epicormic shoots.

Single aerial applications of Bacillus thuringiensis Berliner (Bt) to control infestations of the eastern spruce budworm (Choristoneura fumiferana Clemens) have had varied operational success. Double applications are too expensive for general use, but might prove useful if directed to areas where the initial application was unsuccessful. This requires forecasts of the efficacy of the initial application in operational spray blocks within 4–5 days.

Data were collected in 30 spray blocks in 1989 in a feasibility study to determine if such forecasts of spray efficacy could be made from the prespray budworm population density, N0, and from the proportion of the population that had ingested a lethal dose Bt within 2 days of application, M. A mathematical model forecasting the postspray budworm population density, NF, was derived from population-dynamic considerations and fitted (r2 = 0.48, p < 0.0001):

The proportion of current foliage defoliated, D, depended (r = 0.81) on N0 and on whether the block was sprayed (I = 0) or not (I = 1):

Only one measure of defoliation involved M in any statistically significant way. The predicted (from values of N0) proportion of defoliation prevented by Bt application, dD, was weakly (r2 = 0.25, p = 0.002) related to M:

The large proportion of the variation in efficacy that remains unexplained by the models involving M limits the operational utility of this approach as it now stands for specific sites. The potential for further development of these models as decision support tools for fairly large spray blocks is discussed in terms of improving the sampling plan and including additional predictor variables.

Methods are also presented that reduce bias in calculations of population reduction (Abbott 1925) and foliage protection when data are available from few control and many treatment blocks.

The mean weights of the initial eggs (Ei) of the spruce budworm, Choristoneura fumiferana (Clem.), vary within and between populations. Measurements of collections from across the range of this species reveal the presence of a cline directly related to latitude and longitude of the collection source. Collection mean Ei values range from 0.219 mg in the northwest to 0.157 mg in the southeast. A similar cline, also related to latitude but negative in slope, is demonstrated for the number of eggs per unit pupal weight. This cline also finds expression in changing slope of fecundity/pupal weight regressions. The cline in egg weight appears to be an adaptation to winter conditions across the range of this insect and should be considered in population dynamics.

Detailed estimates of defoliation caused by spruce budworm [Choristoneura fumiferana (Clem.)] over the crown length of young balsam fir [Abies balsamea (L.) Mill.] were made throughout a spruce budworm outbreak from 1976 to 1984 in the Cape Breton Highlands, Nova Scotia. The results show no clear tendency for a particular level of the crown to be damaged more heavily than any other. Thus, there is no reason to continue the common practice of taking samples from the mid-crown level on the assumption that they represent an ‘average’ level of defoliation either for high or low populations. Sampling from the bottom of the crown should provide a more convenient and cost-effective approach for estimating defoliation.

Laboratory studies of the mean weights of initial eggs (Ei) of the spruce budworm, Choristoneura fumiferana (Clem.), show that this value is determined by the genetic constitution of the female moth and is relatively independent of environmental control. Dietary differences experienced by the female during larval development, and originating from different hosts or from reduced nutrient levels in artificial diets, did not affect Ei values; however, depletion of nutrients sufficient to reduce fertility greatly did reduce Ei. Temperature conditions during the ultimate larval and pupal stages influence Ei values which vary inversely. Mean egg weights are strongly heritable and are readily selected for, thereby demonstrating the presence of strong genetic control.

The effectiveness of seven insect juvenile hormone analogs (JHAs) in disrupting metamorphosis of the eastern spruce budworm, Choristoneura fumiferana Clemens, was determined by applying the compounds topically to early sixth-instar larvae and monitoring subsequent development. Fenoxycarb showed promising control potential, with an LC50 of 0.26 μg per insect. Relative lethal effectiveness, based on LC50 values, was Fenoxycarb > ZR9892 > ZR8487 > S-71639 > methoprene > ZR9582 > ZR10151. Some of the JHAs tested may be useful in an integrated spruce budworm control program.

Larvae are reared on a synthetic diet in 1 oz. ribbed plastic cups. To eliminate the task of placing individual larvae on food, small gauze patches containing 25–40 larvae are placed in the cups prior to emergence from hibernacula. Larvae establish feeding sites between the ribs and are relatively undisturbed by others in the cup until the fifth instar. For maintenance of rearing stock the number of larvae is reduced to six to eight per cup, and they are allowed to pupate in the cups. Up to 100 pairs of pupae are placed in screened cages for adult emergence, mating, and oviposition. When the adults emerge balsam fir foliage is introduced and most of the eggs are deposited on the needles. Needles or twigs with egg clusters are transferred to large dishes the inside of which is painted black. The dish is tightly sealed with parafilm to which small gauze patches are attached and then placed under artificial lighting. The newly-hatched larvae are attracted toward the light and spin hibernacula in the gauze. The parafilm and gauze are sealed in plastic bags for cold storage treatment. By this system up to 10,000 larvae per week are easily produced.A discussion on the selection of rearing stock, rearing conditions, rearing containers, and the use of anti-fungal agents is included in the report.

The seasonal damage to female reproductive structures (buds, flowers, and cones) of black spruce, Picea mariana (Mill.) B.S.P., was assessed during 1983 and 1984. Nineteen insects (five Orders) and the red squirrel, Tamiasciurus hudsonicus (Erxleben), were found feeding on these reproductive structures. Collectively, these organisms damaged 88.9 and 53.5% of the cones in 1983 and 1984, respectively. In the 2 years, Lepidoptera damaged 61.8% of the cones in 1983 and 44.4% of the cones in 1984. The spruce budworm, Choristoneura fumiferana (Clem.), and the spruce coneworm, Dioryctria reniculelloides Mut. and Mun., were the most important pests. Cones damaged by Lepidoptera could be classed into three categories: (a) severe, yielding no seeds; (b) moderate, yielding 22.3 seeds per cone; and (c) light, yielding 37.5 seeds per cone. Undamaged cones yielded on average 39.9 seeds per cone. Red squirrels removed 18.8% of the cones in 1983 and none in 1984. The spruce cone axis midge, Dasineura rachiphaga Tripp, and the spruce cone maggot, Lasiomma anthracinum (Czerny), caused minor damage in both years. Feeding by spruce cone axis midge did not reduce cone growth significantly or the number of viable seeds per cone, but feeding by the spruce cone maggot did. During both years new damage by insects to the female reproductive structures of the experimental trees was not observed after mid-July. In 1983 damage by red squirrels occurred from early to late September. In 1984 damage to cones on trees treated with dimethoate was 15.6% compared with 53.5% for untreated trees, without an increase in the number of aborted cones.

Normal matings of Choristoneura fumiferana (Clem.) resulted in the transfer of single, persistent spermatophores. The mean duration of copulation was 4 hours with a range from 21/2 to 81/2 hours. All the first matings of males were fertile and the spermatophores were large, while an increasing proportion of the subsequent matings were infertile and the spermatophores became progressively smaller. Only fertilized females laid normal numbers of eggs. There was no evidence to show that insemination can be accomplished without the transfer of a spermatophore. However, the presence of a spermatophore in the bursa of the female was not always indicative of successful insemination.Males mated only once within a 24-hour period; they were least responsive to females just after emergence (< 0.5 day old) and most responsive when 2 to 4 days old. Females mated most readily when < 0.5 day old and became progressively less attractive or less receptive with age. Mated females were not as attractive as unmated females.

Male and female laboratory reared spruce budworm moths, Choristoneura fumiferana (Clem.), were placed in cages in a conifer forest, and the surrounding air permeated by each of four blends of the E and Z isomers of the sex pheromone (11-tetradecenal) at two concentrations. Mating suppression of 53–83% was found for each blend tested. At one concentration the four suppressions were similar, while at the other only one was significantly different. Electroantennograms (EAGs) were obtained from male moths for each of six E:Z blends at four concentrations. EAGs were similar for most blends at a given concentration, but tended to be larger than at a blend of 0E:100Z.

These results were discussed using a current hypothesis on the ability of males to detect sex pheromone in air containing pockets of different isomeric blends.

Two Sumithion® formulations were sprayed aerially to compare their effectiveness in controlling spruce budworm, Choristoneura fumiferana (Clemens), in balsam fir, Abies balsamea (L.) Mill. Sumithion 20% flowable, a new formulation, and Sumithion technical were applied twice at 210 g AI (in 1.5 L of spray mix)/ha using a Cessna 188 Agtruck equipped with four Micronair atomizers. More than 95% of the technical and <45% of the Sumithion flowable spray droplets were <50 μm in diameter. Larval reduction ranged from 67 to 84% in the Sumithion flowable plots, from 52 to 55% in the Sumithion technical plots, and from 28 to 38% in the untreated plots. Postspray residual populations averaged 4.1, 6.2, and 10.3 larvae per 46-cm branch in the flowable, technical, and untreated blocks, respectively. Defoliation in the Sumithion flowable block averaged 18.5% and was not significantly different from the technical block but both were significantly less (α = 0.05) than that in the untreated block, which averaged 46.2%. The results suggest that Sumithion 20% flowable was more efficacious in controlling spruce budworm than Sumithion technical insecticide.

The control of bud infesting insects presents a problem to which the systemic insecticides theoretically offer a promise of solution. The systemic action of some organophosphorus insecticides has been well demonstrated on many agricultural crops. An excellent bibliography on these and other systemic insecticides has been compiled bv Giang (1954). Anderson (1955), reported mortality of eastern tent caterpillars, Malacosoma americanum (F.) when fed on leaves from wild cherry seedlings grown in soil treated with parathion. Recently, Norris (1960) and coppel and Norris (1960, 1961), reported that some of the newer organophosphorus insecticides show a high degree of insecticidal action in both elm and white pine. In 1960 Dever and Davis reported success of phosphamidon against gypsy moth larvae feeding on white pine. This gave further indication that a systemic insecticide might be effective to defoliators on other conifers. Other investigators have shown that the absorption characteristics of systemic insecticides vary greatly with the soil type, absorption being greatest in sandy soils (Getzin and Chapman 1959, 1960), Zaki and Reynolds (1961)). These findings may be of practical importance in forest insect control since many forest sites are either rocky, sandy, or submarginal agricultural lands, and hence insecticide spray residues of this type may be reabsorbed into the tree.

Summary life table data of historical spruce budworm, Choristoneura fumiferana (Clemens), populations from the Green River Project in New Brunswick, Canada (1947–1958), provided information for developing a management strategy using annual inundative releases of the egg parasite Trichogramma minutum Riley. Three threshold levels (39, 169, and 201 budworm egg masses per 10 m2 foliage) were assigned to the spruce budworm population and a simulation model employed to manage it at or below each level. Based on field data, the lowest threshold represented a light level of defoliation while the other two thresholds represented moderate defoliation levels. With the exception of 3 years at the low level, annual inundative releases of T. minutum successfully suppressed the spruce budworm population below the three thresholds in the model. Annual releases of T. minutum were also simulated during the inclining, plateau, and declining phases of one outbreak cycle of the spruce budworm. At the same rate (12 × 106 female T. minutum per hectare), inundative releases during the inclining phase were more effective than during either the plateau or declining phases. The results suggest that some low and moderate populations of spruce budworm can be effectively managed using annual inundative releases of an egg parasite, particularly toward the end of the inclining phase of an outbreak, but when populations reach severe levels, additional mortality agents probably will have to be considered in an integrated approach.

An illustrated key is given to 28 genera, representing 10 families of at least 50 chalcidoid parasitoids and hyperparasitoids recorded from Choristoneura species (Tortricidae), or their primary parasitoids, in America north of Mexico. We include species reared throughout a 12-year study of the parasitoids and hyperparasitoids associated with the spruce budworm, Choristoneura fumiferana (Clemens), in New Brunswick, Canada, as well as those listed in various catalogs. Notes are provided for all the chalcidoid species, whether or not they are recorded in the literature. Nine species doubtfully or incorrectly recorded from Choristoneura species are also discussed.

Primary parasitoids belonging to the Ichneumonidae, Braconidae, and Tachinidae have been recorded from 10 of the 16 Nearctic Choristoneura species but chalcidoid parasitoids are recorded, usually as hyperparasitoids, from only four of the 16 species. The species of primary parasitoids of Choristoneura checked for records of parasitism by Chalcidoidea are tabulated by host species. Also listed are species of primary parasitoids serving as hosts for each of the chalcidoid species. We report 51 new host records of primary parasitoids and hyperparasitoids from C. fumiferana and its parasitoids collected in New Brunswick.

A new generic combination is given: Mesopolobus tortricis (Brues) comb.nov. from Psychophagus (proposed by Z. Boucek).

The mechanism of sperm precedence in the spruce budworm was studied using a genetic marker. When female moths with red-eyes, a recessive trait, are mated twice within a day, first with a red-eyed male followed by a black-eyed male, three types of offspring were observed in the F1 generation. Some females produced only red-eyed offspring; another group produced only black-eyed progeny; a third group produced a mixture of both types. This indicates that sperms received from either or both matings may be utilized. The time interval between successive sperm transfers appears to be the underlying factor that determines sperm precedence in this insect; a hypothesis to explain this phenomenon is presented.

Field studies in Ontario, Oregon, and California on interspecific attraction and inhibition among the coniferophagous species of Choristoneura (the spruce budworm and its allies) confirmed specific pheromonal differences among the species. Of the three species that are mutually attractive and whose males are attracted by blends of trans- and cis-11-tetradecenal, C. fumiferana, C. biennis, and C. occidentalis, catches of C. fumiferana males in traps baited with C. fumiferana females were significantly reduced by the presence of females from a second group in which it is believed the females produce trans-11-tetradecenyl acetate. Catches of C. occidentalis males by C. occidentalis females were not affected in this way. F1 hybrids and backcrosses between an aldehyde-producing species and an acetate-producing species produced females that were attractive to males of one or other of the parent species, although some females were not attractive to either. Individual females never attracted males of both parent species, and of those that were attractive, more were attractive to males of the aldehyde species than to males of the acetate species. The results suggest sex-controlled inheritance and expression.

Bacillus thuringiensis (Dipel® 36B) mixed with a sublethal concentration of acephate (Orthene®) (O, S-dimethyl acetylphosphoramidothioate), an organophosphorous insecticide, was applied at 2.35–14 l./ha to white spruce (Picea glauca) and balsam fir (Abies balsamea) trees infested with spruce budworm, Choristoneura fumiferana (Clem.). The treatment rate was 20 Billion International Units of B. thuringiensis (B.t.) activity with or without 42 g of active ingredient of acephate/ha.

The ground deposit of the standard Dipel wettable powder formulation was 12% of emitted volume compared with 21–32% for the Dipel 36B flowable. The viability of B.t. spores was drastically reduced after 1 day of weathering but a high level of biological activity by the spore–crystal complex persisted for up to 20 days post-spray due probably to crystal activity.

The addition of about 10% of the recommended operational rate of acephate to the B.t. suspension increased larval mortality by 34% when applied at 4.7 l./ha. Reductions in budworm populations were 97–99% in B.t. + acephate plots and 86–90% in B.t. alone plots.

Plots with moderate budworm densities of up to 27 larvae/100 buds on white spruce and 36/100 on balsam fir were satisfactorily protected from excessive defoliation in the year of spray by B.t. with or without acephate. Plots with higher population densities were not satisfactorily protected based on the branch sample examination but aerial color photographs indicated good protection to the top third of the trees. Population declines were greater and defoliation and oviposition were lower in the treated plots than in the untreated checks 1 year later without further treatment. Two years later the larval population densities in all plots were low but the density was twice as high in the untreated check as in the treated plots, indicating long term suppression by the treatments. Defoliation was negligible in all plots.

The treatments had no deleterious effect on spruce budworm parasitism. The data indicate that the integrated approach using Bacillus thuringiensis – chemical pesticide combinations is a viable alternative to the use of chemical pesticides alone in spruce budworm control. Large scale testing is now warranted.

Mean daily progeny production by Trichogramma minutum (“Maine strain”) was 15.2 in Choristoneura fumiferana and 10.9 in Sitotroga cerealella eggs. Total progeny production was higher in S. cerealella, but not significantly different from that of C. fumiferana eggs. Significantly more eggs were deposited by T. minutum the first day than in subsequent days regardless of host. We found no significant relationship between progeny produced by females and the day of male death as previously reported. Ratio of females:males decreased significantly with increasing age and opposition activity of the mother. The oviposition period spanned 68% of the female's life span when S. cerealella eggs were available; whereas females spent significantly less time (60%) ovipositing in C. fumiferana eggs.

Cytoplasmic polyhedrosis viruses are, in general, more infectious to spruce budworm, Choristoneura fumiferana (Clemens), and forest tent caterpillar, Malacosoma disstria (Hübner), than the nuclear polyhedrosis viruses which affect these insects. The cytoplasmic polyhedrosis viruses interfere with and retard development of the nuclear polyhedrosis viruses.Larvae of both insects, as they grow older, develop resistance to both viruses. Resistance develops more rapidly and to a greater degree against the nuclear polyhedrosis than against the cytoplasmic polyhedrosis viruses.The nuclear polyhedrosis viruses are more lethal than the cytoplasmic polyhedrosis viruses, and all larvae infected with the nuclear polyhedrosis viruses die except those infected so late in larval development that they are able to pupate. Most young larvae infected with the cytoplasmic polyhedrosis virus die or are seriously affected, but infection has progressively less effect as the larvae mature.