The insecticide Foray 48B (Bacillus thuringiensis var. kurstaki Berliner) was applied undiluted at 30 BIU per ha to control spruce budworm, Choristoneura fumiferana (Clem.), in a mixed boreal forest stand of balsam fir, Abies balsamea (L.) Mill., and black spruce, Picea mariana (Mill.) B.S.P. When the treatment was timed to coincide with the early flushing of balsam fir shoots, the corrected budworm population reductions were 74 and 52% on balsam fir and black spruce, respectively. This treatment resulted in 19 and 8% defoliation on the two respective species. When the insecticide application was timed later to coincide with the late flushing of black spruce shoots the corrected population reductions were 93% on balsam fir and 72% on black spruce. Defoliation of the two species was 29 and 10% respectively, following this treatment. Larval survival on both species after the spray timed for black spruce (0.8 and 2.2 larvae per 45-cm branch on balsam fir and black spruce, respectively) was significantly less (P = 0.05) than that observed after the spray timed for balsam fir (4.6 and 4.2 larvae per 45-cm branch on the respective host species).The data indicate that the spray timed to correspond with the flushing of black spruce was generally more efficacious than the spray timed to impact on newly flushed balsam fir; nevertheless, the results raise the question as to how B. thuringiensis insecticides impact on early-instar budworm larvae when there is no preferred current year foliage on which the insects can feed.

Tests of sexual isolation indicate that, in the absence of temporal and spatial isolation, the strict mating behavior of the females and the high sexual aggressiveness of the males of Choristoneura fumiferana (Clem.) would obstruct any inward flow of genes from either C. occidentalis Free, or C. biennis Free. Under these same conditions, however, the two latter species may receive genes from C. fumiferana, since, in tests, their females mated indiscriminately and their males were less aggressive than those of C. fumiferana.

The world is astoundingly variable, and organisms – from individuals to whole communities – must respond to variability to survive. One example of nature’s variability is the fluctuations in populations of spruce budworm, Choristoneura fumiferana Clemens (Lepidoptera: Tortricidae), which cycle every 35 years. In this study, we examined how a parasitoid community altered its parasitism of budworm and other caterpillar species in response to these fluctuations. Budworm and other caterpillar species were sampled from balsam fir (Pinaceae) in three plots for 14 years in Atlantic Canada, then were reared to identify any emerging parasitoids. We found that the parasitoid community generally showed an indiscriminate response (i.e., no preference, where frequencies dictated parasitism rates) to changes in budworm frequencies relative to other caterpillar species on balsam fir. We also observed changes in topology and distributions of interaction strengths between the parasitoids, budworm, and other caterpillar species as budworm frequencies fluctuated. Our study contributes to the hypothesis that hardwood trees are a critical part of the budworm–parasitoid food web, where parasitoids attack other caterpillar species on hardwood trees when budworm populations are low. Taken together, our results show that a parasitoid community collectively alters species interactions in response to variable budworm frequencies, thereby fundamentally shifting food-web pathways.

The newly named C. biennis has a two-year cycle characterized by a second period of diapause at the end of the third instar. Second diapause occurs to varying degrees in C. fumiferana, C. occidentalis, C. orae, C. pinus pinus, and many of their hybrids, but has not been recorded in C. viridis. Although the incidence of second diapause can be influenced by the length of photoperiod to which larvae are exposed after completion of the second-instar diapause, second diapause occurring naturally is not primarily under environmental control. Laboratory studies have demonstrated differences in the incidence of second diapause manifested by these species and by some of their hybrids that point to the existence of genetic differences between them. This evidence supports the newly gained taxonomic status of these insects.

Detailed laboratory studies of mated spruce budworm (Choristoneura fumiferana (Clem.)) show that the number of eggs per day, mean cluster size, and mean wet weight of the eggs gradually decrease during the period of oviposition of individual moths. The term mean weight of initial eggs (Ei) is defined and compared with other measurements of mean egg weight based on total egg complement or parts of it. Ei is 6%–12% greater than the mean egg weight based on all eggs laid. In spite of variation in pattern of egg weight distribution among moths, Ei appears to express satisfactorily the differences in mean egg weight among moths and can be used to survey egg weights among populations.

Laboratory rearing studies of individual clusters indicate slightly slower emergence rates (seconds from hibernacula), greater survival, and smaller proportions of male pupae in the third and fourth quartiles of the egg complement; there were no differences in pupal weights related to cluster order. There is no ready explanation for this improved survival of larvae from eggs known to be smaller.

Implications of these results for the population dynamics of the spruce budworm are discussed. The more stressful conditions encountered in the natural environment may counteract the apparently better survival of individuals from the latter part of the egg complement.

The roles of adult activity patterns and sex pheromones were investigated in the sexual isolation of Choristoneura fumiferana and C. pinus, species which hybridize in cages but not in the field. Female C. fumiferana started calling (extruding the sex pheromone gland) earlier (50% of the females started calling by sunset) than female C. pinus (50% by 11/2 hours after sunset). Male C. fumiferana were also attracted to traps by the females earlier, although the times of the peak catches were approximately the same in both species. Males, both in the laboratory and the field, responded only to the sex pheromone of their own species. It is therefore concluded that while C. pinus adults normally appear about 2 weeks later than those of C. fumiferana, which reduces the possibility of hybridization, when the adults do overlap, the ultimate barrier is the specificity of the sex pheromones.

A larval population of spruce budworm, Choristoneura fumiferana (Clemens), was monitored for 5 d following aerial application of a commercial formulation of Bacillus thuringiensis Berliner subsp. kurstaki to investigate dose acquisition and expression (larval mortality, recovery, feeding, and growth) in relation to spray deposition and persistence of spray deposits. The main objective was to test if previous laboratory observations on how B. thuringiensis affects feeding and dose ingestion by spruce budworm larvae hold true under field conditions. About 40% of the treated population ingested a lethal dose within 1 d after spray application. Lethally dosed larvae died without further feeding upon transfer from treated foliage to (untreated) artificial diet. Resumption of feeding by larvae that survived the treatment was delayed relative to larvae from the control population during 3 d following spray application; during that time, normal feeding activity and larval weight gain were suppressed. Inhibited feeding by survivors appeared to prevent further dose uptake because the proportion of lethally dosed larvae in daily collections did not increase despite significant residual spray deposits in budworm feeding sites. Restoration of "normal" recovery times by the fourth day coincided with a 65–85% reduction in persistence of the pathogen on the foliage and did not result in further lethal dose acquisition, as treatment-induced mortality dropped to about 20% on the 4th and 5th days. The observations are consistent with previous laboratory observations of how B. thuringiensis affects larval feeding and with the hypothesis that feeding inhibition may be a limiting factor in the acquisition of a lethal dose.

The acute toxicities of an extract obtained from a plant within the Piperaceae family and related synthetic analogues were tested against four common Canadian forest pest insects. The acute toxicity of the extract from black pepper, Piper nigrum L., was assessed after 1, 24, and 72 h by the percent larval mortality. The 24 h LC50 estimates for the P. nigrum extract were (in order of decreasing sensitivity) 0.012% for the introduced pine sawfly, Diprion similis (Hartig) (Hymenoptera: Diprionidae), 0.053% for the forest tent caterpillar, Malacosoma disstria Hubner (Lepidoptera: Lasiocampidae), 0.282% for the gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), and 0.998% for the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Torticidae). There was no significant increase in mortality after 72 h. Seventy percent of L. dispar larvae dropped off or moved from branches within 1 h of application of 0.2% P. nigrum extract, indicating that these compounds have a repellent effect. Pipercide and nor-pipercide were more toxic to L. dispar and M. disstria larvae than piperolein A and a P. sarmentosum Roxb. amide 72 h after either oral or topical administration of these compounds. Toxic effects of piperamides were more pronounced by oral ingestion. Ninety percent mortality of L. dispar larvae occurred following an oral dose of 5 µg pipercide in diet, whereas mortality was only 40% following topical treatment at 5 µg pipercide/insect. Whole Piper extracts might be useful for the control of sawflies and tent caterpillars in small-scale applications, based on the demonstrated efficacy and reduced risk potential.

Laboratory studies of seven North American Choristoneura species and two subspecies from widely distributed locations demonstrate the low level of genetic separation among them. No differences were found in numbers (n = 30) or morphology of chromosomes among members of the group or in any of the hybrids examined. High levels of mating success were obtained in all inter se matings as well as in crosses and back-crosses. However, mating success was greater for crosses within host type and within pheromone type than for crosses between types. Viability and fertility were similar in all the hybrids and close to those of the inter se progenies. Mean weights of initial eggs varied by a factor of 2 from the lowest (C. pinus Freeman) to the highest (C. lambertiana ponderosana Obraztsov). Mean weights of initial eggs produced by hybrids were generally close to those of the parental species. However, when one parent was C. fumiferana (Clem.), mean weights of initial eggs were either much larger (male C. fumiferana) or much smaller (female C. fumiferana) than either parental type. These differences could affect survival of some progeny under harsh conditions. This evidence supports other studies in indicating that C. fumiferana is genetically distinct from other species in this group.

The western spruce budworm, Choristoneura occidentalis Freeman (Lepidoptera: Tortricidae), is an important pest of western North American coniferous forests, where its principal larval host is Rocky Mountain Douglas-fir, Pseudotsuga menziesii subspecies glauca (Beissner) Murray (Pinaceae). In southwestern Alberta, Canada, populations were recently discovered feeding on an unconventional host, an Engelmann spruce, Picea engelmannii Parry ex. Engelmann × white spruce, Picea glauca (Moench) Voss hybrid (Pinaceae), in a transition zone between the two major forest types characterised by these conifer species. We use molecular evidence to verify the species identity of outbreaking Choristoneura populations collected from Douglas-fir and hybrid spruces in southwestern Alberta in 2009, and characterise the larval and male moth phenology. Both mitochondrial and microsatellite markers confirmed these populations as C. occidentalis, but admixture with Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae) was detected in some individuals. Few differences associated with separate host trees were evident in the phenology of larvae and the flight period of male moths.

UC-62644, a moult-inhibiting insect growth regulator (IGR) belonging to the benzoylphenylureas, had an EC50 of 0.1 to 0.2 ppm in a meridic diet for the 3rd to 6th larval instars of the spruce budworm, Choristoneura fumiferana Clemens. The effects of the IGR were apparent in less than 48 h after ingestion and there was evidence for some contact toxicity. The larvae were unable to discriminate between IGR-treated and untreated diet. Experimental aerial application of the IGR revealed that at <70 g in 4.7 1/ha (1 oz in 0.5 U.S. gal/acre) it effectively controlled spruce budworm populations and afforded foliage protection. These results were comparable with those obtained with Matacil® applied at the recommended rate.

Priesner (1979) reported five types of receptor in the trichoid sensilla on the antennae of male spruce budworm, Choristoneura fumiferana. One responded maximally to (E)-11-tetradecenal (Ell-TDAL), the primary component of the natural sex pheromone (Sanders and Weatherston 1976). Two other receptors showed maximum response to (E)- 11-tetradecen-1-yl acetate (E 11-TDACET) and (E)- 1l-tetradecen- 1-ol (E11-TDOL), respectively, both of which are present in female glands, but neither of which has been found in significant amounts in the emitted pheromone. The other two receptors showed maximum responses to (E)-9-tetradecenal (E9- TDAL) and (E,E)-9, 11-tetradecadienal (E9, E 11-TDDAL), respectively, neither of which has been reported from gland extracts or the emitted pheromone.

Artificial diet is commonly used to rear the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae), in the laboratory. While its effect on spruce budworm performance is relatively well studied, no information exists about the influence of rearing diet on larval parasitism. In this study, spruce budworm larvae reared in the laboratory on artificial diet or balsam fir, Abies balsamea (Linnaeus) Miller (Pinaceae), foliage were introduced in the field to compare parasitism. Additionally, a laboratory choice test was conducted with the larval parasitoid Tranosema rostrale (Brischke) (Hymenoptera: Ichneumonidae). No significant influence of spruce budworm rearing diet on parasitism in the field was found. However, in the laboratory, T. rostrale attacked significantly more foliage-fed larvae. We conclude that even if initial differences in parasitism may exist between diet-fed and foliage-fed larvae in the laboratory, spruce budworm larvae reared on artificial diet can be used in field studies investigating parasitism of wild spruce budworm populations without concern that the food source would affect parasitism.

Flight durations of male spruce budworm moths, Choristoneura fumiferana (Clem.), that were locked-on to pheromone plumes from female moths were measured in a wind tunnel. Flight was sustained by use of a movable patterned ceiling. The longest sustained flight was 53 min. The effects of different background concentrations of synthetic pheromone were tested by surrounding the female moths with rubber septa loaded with synthetic pheromone. The duration of sustained flights decreased as the concentration of background synthetic pheromone increased, but at all concentrations some males persisted in orientated flight for 10 min or longer.

Where the insecticide Zectran was used to protect foliage from feeding of the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae), the per cent parasitism of dipteran parasitoids (Tachinidae) showed a statistically significant lower value. In treated areas, the per cent parasitism of the hymenopteran Ephialtes ontario (Cresson) (Ichneumonidae) was lower; Meteorus trachynotus Viereck was about the same; Apanteles fumiferanae Viereck, Glypta fumiferanae (Viereck) (Braconidae), and Trichogramma minutum Riley (Trichogrammatidae) were greater. None of these differences was statistically significant. Results were consistent for the 2 years of study with the exception of E. ontario which showed a significant lower percentage parasitism in areas treated 1 year. Absolute population numbers of parasitoids were lower than is suggested by comparisons of apparent parasitism levels. The lowest absolute numbers were found in tachinids and E. ontario. Parasitic hymenopterans and dipterans were among the adult insects killed by the aerial application of Zectran but none of the species collected was a major spruce budworm parasitoid.

Development rates of the parasitoid, Trichogramma minutum Riley, were studied to provide information required in timing field releases of T. minutum for suppression of egg populations of the spruce budworm, Choristoneura fumiferana (Clemens). Development was observed in eggs of 2 host species, C. fumiferana and Sitotroga cerealella (Olivier), at constant temperatures of 14, 21, and 27 °C. Parasitoid development varied directly with temperature. Parasitoids developed more rapidly in eggs of S. cerealella than in those of C. fumiferana. Parasitoid males developed faster than females in some host-temperature treatments. Development of T. minutum is apparently rapid enough to allow progeny of parasitoids released early in the spruce budworm's oviposition period to mature and be available to oviposit in budworm eggs deposited later in the budworm oviposition period. Potential release strategies are discussed.

Airplane application of the insect growth regulator CGA 13353, a juvenile hormone mimic used experimentally against spruce budworm, Choristoneura fumiferana (Clem.), did not drastically reduce percentage parasitism in field samples of that host, but there was some evidence of susceptibility. Exploratory sampling of maple defoliators suggested that one species and its parasitoids suffered some mortality, but another species and its parasitoids did not. The treatment did not influence the viability of ant colonies.

A dual-choice behavioral bioassay and gas chromatography – electroantennogram detection (GC–EAD) were used to determine the effect of host terpenes and nonhost green-leaf volatiles (GLVs) on the oviposition preference of the spruce budworm, Choristoneura fumiferana (Clemens). Some emphasis was placed on assessing the ability of females to distinguish between enantiomers of chiral monoterpenes because (+)-α-pinene but not (–)-α-pinene or (±)-α-pinene had been shown previously to promote oviposition. Headspace volatiles from white spruce, Picea glauca (Moench) Voss (Pinaceae), and balsam fir, Abies balsamea (L.) Mill. (Pinaceae), were sampled using solid-phase microextraction and identified by gas chromatography – mass spectrometry with the aid of a chiral column. Females deposited significantly more egg masses on filter paper substrate treated with host monoterpenes than on controls. Contrary to expectation, substrates treated with several GLVs were also preferred over the controls. None of the GLVs or terpenes was deterrent. Females showed no significant ability in either the behavioral or the GC–EAD bioassays to distinguish between enantiomers of selected chiral monoterpenes, including α-pinene, in contrast to earlier findings. We conclude that host terpenes serve as general rather than host-specific oviposition stimuli for spruce budworm.

Two new species of the mite family Erythraeidae (Acari: Prostigmata: Parasitengona) found associated with the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae), in Maine are described. Larvae of Leptus treati sp.nov. parasitize spruce budworm adults; L. treati is the first member of the genus to have both larval and postlarval instars described. Adults of Balaustium kendalli sp.nov. prey on spruce budworm eggs; B. kendalli is only the second member of the genus to have both larval and postlarval instars described.

A droplet-imbibing assay was used to assess the susceptibility of third-instar larvae of the spruce budworm, Choristoneura fumiferana Clemens, to Foray 48B, a commercial formulation of Bacillus thuringiensis subsp. kurstaki containing 12.7 billion international units (IU) per litre. We observed an LD50 of 1.17 IU/larva for third instars, as compared with 3.96 IU/larva for fifth instars. Comparison with previously published data on susceptibility of later instars revealed that third instars were two-to three-fold more susceptible to Foray 48B than fourth and fifth instars and about eightfold more susceptible than sixth instars. Vulnerability of third instars to simulated aerial spray deposits was investigated by using potted balsam firs, Abies balsamea L. Potted trees were infested in the greenhouse when the buds were starting to swell, using a density of about one newly emerged second-instar larva per bud. When 90% of the larvae had reached the third instar and 52% of the buds were breaking (4 d after infesting), infested twigs were harvested and sprayed with undiluted Foray 48B in a spray chamber. Spray droplets on the buds measured between 25 and 125 μm in diameter, with 80% having a diameter of 80 μm or less. A density of 4.2 ± 1.0 droplets per bud resulted in spruce budworm mortality of 83.4 ± 4.0% and a corresponding reduction in larval density of 86.5 ± 3.9% (means ± SD, n = 6) after 5 d at 25 °C. Results of the spray chamber test suggest that third-instar spruce budworms were able to acquire a lethal dose, despite their concealed feeding habits.