Abstract: The host-finding responses of the egg parasite,Trichogramma minutum Riley, reared from its natural host,Choristoneura fumiferana (Clemens) and a laboratory host,Sitotroga cerealella (Oliver), to hexane extracts of scales of these hosts were compared in laboratory experiments. When presented withC. fumiferana eggs on filter papers treated with hexane and hexane extract of grain moth scales, egg finding byT. minutum was random. When presented with budworm eggs on filter papers treated with hexane and hexane extract of budworm scales,T. minutum found significantly more eggs on extract-treated filter papers, indicating the presence of kairomones on the scales of spruce budworms.T. minutum responded to kairomone-treated patches with a localized search behavior characterized by intense antennal tapping, decreased locomotion and increased turning within the patch, and repeated returns to the patch. In the absence of successful host finding, this response slowly waned. No significant difference in behavior ofT. minutum reared on eitherC. fumiferana orS. cerealella was observed.

Abstract: The biosynthesis of a large number of sex pheromone components of various moth species has been shown to start with common fatty acids and involve chain shortening by two carbons and introduction of a double bond at the 11–12 position. A recent report indicates that one of these common components, (E)-11-tetradecenyl acetate, is present in the eastern spruce budworm,Choristoneurafumiferana, but is not made by this pathway. Reinvestigation of this insect using in vivo and in vitro techniques indicates that the acetate indeed is made by a sequence of reactions similar to that used in other leafroller moths. In fact, evidence was found for the presence of several Δ11-desaturase systems in spruce budworm. One produced a large quantity of (Z)-11-hexadecanoic acid, and another produced (E)-11-tetradecanoic acid. It is not known if the small amount of (Z)-11-tetradecanoic acid is produced by either of those two systems or by a third system. A comparison with other species showed that cabbage looper moths have only the first system, redbanded leafroller moths use the last two systems, and European corn borer moths have all three.

Abstract: High concentrations of synthetic sex pheromone caused increased flight activity among mated female spruce budworm of all ages, a fact that may indicate an increase in dispersal. Flight activity also increased among older virgin females, but not among females one day old, the age at which they usually mate. Receptivity of young virgin females to courting males was not affected by pheromone-permeated air. Synthetic sex pheromone is therefore not likely to influence mating frequency through its effects on female activity.

Abstract: The infection of spruce budworm larvae by the fungus Entomophaga aulicae was studied by light, scanning, and transmission electron microscopy. Exposure of the larvae to conidia resulted in the deat...

Abstract: Eighty one standard ferilizer trials were established in unmanaged. middle-aged stands of jack pine, black spruce, white spruce, red spruce and balsam fir in Nova Scotia, New Brunswick. Quebec, Ontario, Manitoba. Saskatchewan and Alberta. The 5-year and 10-year total volume responses, based on conventional plot remeasurements, are summarized for installations grouped by Forest Section. A complete report is being published separately. Jack pine stands were most consistently responsive to nitrogen additions; black spruce, red spruce and white spruce and balsam fir were much more variable in response. Spruce budworm defoliation and natural tree mortality resulted in very low or negative net increments for many installations. Where P or K was added with N additional response appeared small. Fertilizer efficiencies of 7 to 35 kg of applied nitrogen per cubic meter of additional response were indicated: recommendations are made for further work on fertilizer response.

Abstract: Inactivation rates of Bacillus thuringiensis were determined for two formulations applied at 20 and 30 billion international units/ha by helicopter against the western spruce budworm, Choristoneura occidentalis Freeman. The number of days before spray residues declined to 50% of original activity varied with the dosage. Because inactivation rates of the four treatments were approximately equal, success of a B. thuringiensis control program apparently depends more on the initial rate of larval mortality than on the persistence of the microbial agent.

Abstract: Parasite studies were conducted during a field test of two Bacillus thuringiensis Berliner formulations (Thuricide 32LV and San-415), each applied at two dosages (20 and 30 billion international units per hectare) against western spruce bud worm (WSBW), Choristoneura Occidentalis Freeman, to determine possible adverse effects of B. thuringiensis on WSBW natural enemies. Microscopic examination showed that three parasite species contained B. thuringiensis: Glypta fumiferanae (Viereck), Apanteles fumiferanae Viereck, and Phytodietus fumiferanae Rohwer. Occurrence of parasites infected or contaminated with B. thuringiensis was extremely low and did not seem to be related to any of the treatment applications. In rearings of almost 12,000 WSBW larvae, neither percentage of parasitism nor species distribution of parasites differed significantly between control and B. thuringiensis -treated plots throughout the sample period. The parasites attacking preoverwintering WSBW larvae, G. fumiferanae and A. fumiferanae , were the most abundant species collected.

Abstract: Three species of eumenid wasps, Ancistrocerus adiabatus (Saussure), Ancistrocerus antilope (Panzer), and Euodynerus leucomelas (Saussure), accepted and provisioned predrilled wooden blocks placed in a spruce-fir forest of Maine. The eumenids preyed on late instars of the spruce budworm, Choristoneura fumiferana (Clemens), and on other lepidopterous defoliators. Spruce budworm accounted for 94% of provisioned prey. There was no significant difference in acceptance among trap-nesting blocks at four heights (0.0, 0.5, 1.0, and 1.5 m). However, there was a trend toward increased acceptance of blocks at 0.5 m.

Abstract: During 1982 and 1984, ground releases of Trichogramma minutum Riley were assessed for control of the spruce budworm, Choristoneura fumiferana (Clemens), on 12- to 20-year-old, white spruce stands in northern Ontario. Maximum parasitism of susceptible egg masses was 16 and 87% following the release of 480 000 and 12 million female T. minutum per hectare, respectively. Releases at intervals of 1 week maintained parasitism of susceptible egg masses at constant levels throughout the oviposition period of spruce budworm. When parasitism of susceptible egg masses was maintained above 78.2% during the ovipositional period, total egg mass parasitism averaged 58.0% and resulted in an 80.3% reduction of overwintering 2nd-instar larvae. The optimal strategy for reducing spruce budworm was two releases of T. minutum at an interval of 1 week in the ovipositional period. This allowed a second generation of parasitoids to emerge from the spruce budworm eggs that were more efficient in maintaining high levels of parasitism than those emerging from the standard rearing host. Natural parasitism of spruce budworm egg masses was less than 4% and there was no carryover of parasitism in the years following inundative release. The rate of T. minutum release necessary to achieve effective mortality of spruce budworm during outbreak populations is discussed briefly.

Abstract: Five formulations of the primary sex pheromone components of the spruce budworm (Choristoneura fumiferana [Clem.]) were evaluated as lures for monitoring spruce budworm populations: Biolures (Consep Membranes Inc.), Luretape plastic flakes (Hercon, Healthchem Corp.), polyethylene vials (International Pheromone Systems), hollow fibers (Albany International), and polyvinyl chloride (PVC) pellets. PVC pellets showed significant loss in attractiveness over the required 6-week period. Also, different batches of PVC pellets had very different rates of pheromone release and attraction; the oldest lures, stored for the longest period, were the most attractive. Luretape caught fewer moths than anticipated from the release-rate data and showed wide variation in catch among individual lures. Fibers were inconsistent. Biolures and polyethylene vials showed the lowest decline in attractiveness over time and the lowest variation in catch among individual lures, but their capture rates were higher than necessary.

Abstract: One-hundred paired branches, half with dwarf mistletoe plants and half without, were sampled from 100 Douglas-fir in five stands defoliated by the western spruce budworm. The budworm completely defoliated new shoots and buds of all branches sampled including those infected by dwarf mistletoe. Radial growth of host trees (Douglas-fir) was significantly less during the budworm outbreak compared with a similar period before the outbreak. Nonhost trees (ponderosa pine) showed significantly more radial growth during the outbreak than before it. Regression analyses showed that decreases in radial growth were associated primarily with increases in dwarf mistletoe severity (R² = 16.2-18.1). Trees within all dwarf mistletoe infection classes were defoliated by the budworm, and the additional growth reduction caused by defoliation was not significantly different among dwarf mistletoe severity classes. For. Sci. 33(3):767-773.

Abstract: Three species of eumenid wasps, Anci trocerus adiabatus, Ancistrocerus antilope, and Euodynerus Ieucomelas, accepted and provisioned trap-nesting blocks with lepidopterous larvae, A pyralid. Nephopteryx sp., was the most commonly provisioned prey. A. adiabarus and E. leucomelas preyed on late instars of the spruce budworm, Ch istoneura jumiferana: however. budworms accounted for only 6% of the provisioned prey. Estimates of budworm population densities before and after wasp predation, and subsample-s of provisioned prey indicated no significant reductions i = 0.065%) i budworm populations attributable to trap-nesting wasps.

Abstract: Cambial electrical resistance in 10 balsam fir (Abiesbalsamea (L.) Mill.) and 10 white spruce (Piceaglauca (Moench) Voss) trees in Quebec was measured 42 times during July and August 1985. Simultaneous measurements of relative humidity and temperature were also taken so that water potential in air (ψa) could be determined. In both species, cambial electrical resistance, corrected to a constant temperature of 15 °C (CERCOR), was negatively correlated with ψa. On the other hand, 10 measurements on 14 balsam fir trees that had been severely defoliated by the spruce budworm (Choristoneurafumiferana (Clem.)) in 1983 and 1984, and 12 measurements on 14 protected trees showed that the correlation was stronger for sprayed trees than for those that had been defoliated. We propose that the correlation coefficient between cercor and ψa may be a useful index of tree vigor. However, in situations where plots can be visited only once during the season, cambial electrical resistance measurements should be made in the mo...

Abstract: To render Bacillus thuringiensis Berliner suitable for widespread use in spruce budworm, Choristoneura fumiferana Clemens, control, it was necessary to achieve significant improvements in reliability and efficacy along with significant reductions in its cost. In the Maine spruce budworm program, progress in these areas made B. thuringiensis cost-competitive with chemical insecticides by the mid 1980's. Total cost of applying B. thuringiensis fell by two-thirds from 1980 to 1985. Intensive work by manufacturers, university and federal scientists, and spray program managers, facilitated by extensive regionwide sharing of information, contributed to this result. Introducing forestry pesticides to operational use is currently taking too long. Cuts in federal forestry budgets have reduced our capacity to solve these problems in the future.

Abstract: Several compounds derived from aucubin and catalposide were prepared and tested for spruce budworm antifeeding activities. Definite biological activity was observed for compound 11.

Abstract: The relationship between a braconid parasitoid, Apanteles fumiferanae, and a microsporidian pathogen, Nosema fumiferanae, two larval parasites frequently coincident in the spruce budworm, Choriston...

Abstract: The parameter values of a simple dynamical model of a non-even age forest-insect ecosystem are estimated for the case of balsam fir forests and the eastern spruce budworm. It is shown that, despite its extreme simplicity, the model can reproduce time series of a real budworm outbreak and can be considered a compact presentation of available forest data. Strengths and weaknesses of the model are discussed and some directions for further research proposed.

Abstract: Four types of spruce budworm pheromone lures were tested to compare field longevity and efficiency. Biolures with three different pheromone release rates and Silk-PVC lures all caught male budworm moths throughout the moth flight period in proportion to the different release rates. Fumigant strips in traps to kill trapped moths were necessary.

Abstract: Epidemic levels of the western spruce budworm (WSB), Choristoneura occidentalis Freeman, caused average tree defoliation in west central Idaho to increase from 35% in 1984 to 83% in 1985. Associated with this increase in defoliation was a change in relative stand ranking of defoliation between the 2 yr. WSB was found to damage all types and developmental stages of reproductive structures of Douglas-fir. Differential selection of feeding sites was observed, with a significantly higher proportion of larvae found in seed-cone buds than in pollen-cone buds. Of cones examined, 76% were infested with larvae, with the average percentage of destroyed seeds per tree exponentially related to the average current defoliation of the tree. However, even in heavily defoliated trees, some potentially viable seed remained.

Abstract: The neuromorphology of the brain and suboesophageal ganglion (SOG) of the adult male spruce budworm, Choristoneura fumiferana (Clemens), is described and compared with information in the existing l...