Spruce Budworm Populations Research Articles

Numerical Behavior of Some Western Spruce Budworm (Lepidoptera: Tortricidae) Populations in Washington and Idaho

The numerical behavior of populations of the western spruce budworm, Choristoneura occidentalis Freeman, was analyzed by using life table data from north-central Washington and central Idaho. The survival rate of instars IV through VI was lowest at budworm densities below ca. 10 4th instars per m 2 of foliage. This rate was fairly stable (0.2 to 0.6) across higher densities (10 to 40 per m 2 of foliage). The survival rate of pupae from predation increased from ca. 0.2 among the least dense populations to ca. 0.8 among the most dense ones. Survival among the remaining pupae was systematically lower among the populations in Washington than among those in Idaho. The survival rate of eggs and instars I to III was not a function of budworm egg density, place, year, or host species. When density was low, observed egg density was sometimes greater than the ability of resident females to produce eggs. Conversely, at high densities observed egg density was always lower than the egg-laying potential of resident, emerging females. Adult female behavior, together with a generally positive relation between density and subsequent survival during the large larval and pupal stages, may profoundly influence the population dynamics of this pest.

AN OVIPOSITION MODEL FOR THE SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE)

AbstractA process-oriented model was developed to describe the oviposition of the spruce budworm, Choristoneura fumiferana (Clem.), on an individual and a population basis. The model simulates the effects of temperature on female longevity, oogenesis, and oviposition. The model is structured for ease of incorporation of additional processes such as emigration, immigration, mating, and other behavioral reductions in oviposition activity. Simulation results, at both the individual and the population levels, are compared with laboratory and field data. This model is an element of a model of spruce budworm biology currently under development but, by itself, can be used to study the effects of temperature and dispersal on the fecundity of spruce budworm populations.

Bird Predation and Spruce Budworm Populations

Abstract In northern New England, numbers of birds and amounts of budworm (Choristoneura fumiferana) larvae and pupae eaten per bird increased as insect populations increased. Birds ate approximately 2, 23, and 87 percent of the epidemic, transitional, and endemic populations. Blackburnian and Nashville warblers, golden-crowned kinglets, white-throated sparrows, and black-capped chickadees were important predators in stands with endemic budworm populations. Bird communities most effective as budworm predators are found in mature managed forests containing a mix of species and size classes with scattered openings and patches of regeneration.

Analysis of the Regional Dynamics of Unsprayed Spruce Budworm (Lepidoptera: Tortricidae) Populations

An analysis was performed on spruce budworm, Choristoneura fumiferana (Clem.), density and balsam fir, Abies balsamea (L.) Mill., damage data collected annually from 1975 to 1980 at ca. 1,000 locations throughout Maine's Spruce-Fir Protection district. Although general trends could be detected in mean egg density as a function of previous egg densities or defoliation, there was large variability associated with data from different blocks of forest. Mean egg densities for a given level of defoliation were shown to be substantially lower in the southeast part of Maine than in the northwestern region. Mean egg densities in year t + 1 for a given egg mass density in year t were unusually high in 1978 to 1979. Stands with a history of heavy budworm damage were more likely to sustain high egg densities than comparable stands with histories of light damage. This result does not support the hypothesis that dispersing budworm moths tend to lay more of their eggs in lightly damaged stands.

Efficacy of Two Formulations of Bacillus thuringiensis on Populations of Spruce Budworm (Lepidoptera: Tortricidae) on Balsam Fir in Wisconsin1

The efficacy of Thuricide 16B and Dipel 4L formulations of Bacillus thuringiensis Berliner var. kurstaki was determined on Choristoneura fumiferana (Clemens) infestations on balsam fir, Abies balsamea (L.) Mill., in northern Wisconsin. Both formulations reduced budworm populations and protected foliage sufficiently to warrant further field testing with different dosages and gallonage. The B. thuringiensis did not adversely affect parasitism, as determined by laboratory rearing of field-collected larvae.

LABORATORY AND FIELD EVALUATION OF A FAST-ACTING INSECT GROWTH REGULATOR AGAINST THE SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE)

AbstractUC-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.

Nonsaturating Traps and Long-Life Attractant Lures for Monitoring Spruce Budworm Males12

The trapping efficacy of various nonsaturating, pheromone-baited traps was contrasted with standard sticky traps for males of Choristoneura fumiferana (Clemens). Several nonsaturating designs that employed a vaporous insecticide (dichlorvos) were comparable in terms of trap catch to fresh sticky traps. Such nonsaturating traps may prove useful in programs to monitor spruce budworm population dynamics. Commercial formulations of ( E ) and (Z)-11-tetradecenal (ca. 97:3) in a plastic laminate or hollow fibers proved effective over several weeks in luring males.

Time‐delay, diffusion and advection in a model for the time evolution of a spruce budworm population

Abstract We illustrate the use of a two‐time scales (singular perturbations) method for the construction and stability analysis of limit cycle operation in a model‐problem for the time evolution of a spruce budworm population when diffusion and advection processes compete with time‐delays.

VARIABLES ASSOCIATED WITH PHEROMONE TRAPS FOR MONITORING SPRUCE BUDWORM POPULATIONS (LEPIDOPTERA: TORTRICIDAE)

AbstractThe effects of three trap variables (age, saturation, and density) on catches of male spruce budworm moths were tested using Pherocon 1CP® traps baited with synthetic sex attractant in high-density budworm populations in Maine and low-density populations in Ontario. As trap age increased, the number of moths captured decreased significantly; traps aged 2, 10, and 16 days caught an average of 5.4, 28, and 27% fewer moths than unaged traps. Traps functionally saturate and trapping efficiency diminishes in both high and low density populations after ca. 50 moths are caught, although maximum observed catch was 193 moths/day. Density or spacing of traps also affects trap efficiency. Traps spaced 5 m apart may act as a single attraction source. Interference between traps was evident for traps spaced 10, 20, and 30 m apart, while traps spaced at 40 m had the least interference. However, interference at all spacings was noted during peak moth flight in 1978 when mean catch was ca. 140 moths/trap/day.Pherocon 1CP traps can be used for detecting and monitoring spruce budworm populations; however, influences of trap age, timing of trap placement, trap saturation, spacing of traps, and lure strength should be taken into account.

Prevalence of Entomophthorales mycoses in Populations of Spruce Budworm, Choristoneura fumiferana12

Larval and pupal populations of the spruce budworm, Choristoneura fumiferana (Clemens), were sampled for natural prevalence of fungal pathogens in northern Maine during 1975–77. Three species were isolated and identified: Entomophthora sphaerosperma Fresenius, E. egressa Mac-Leod and Tyrrell, and a species of Conidiobolus Brefeld. Prevalence of these pathogens was shown to vary with sample location, crown position of the host, host density, host instar, and temperature and relative humidity trends. Lower crown samples yielded significantly higher fungal disease prevalence. Significantly higher disease prevalence was also found in more dense spruce bud worm population samples. E. sphaerosperma occurred on hosts with a mean between larval instars 5 and 6 (5.79) compared with a mean between the 6th instar and the prepupal stages (6.69) for E. egressa , and a mean between the prepupal and pupal stages (7.10) for Conidiobolus sp . Cool, wet periods of weather appeared to enhance disease prevalence. These findings were examined in terms of entomopathogen epizootiology. The lower crown level and higher host population density may provide an environment more amenable to the spread of disease.

Maine's Spruce Budworm Program: Moving toward Integrated Management

Abstract Epidemic populations of spruce budworm, Choristoneura fumiferana (Clem.), infest a large portion of the spruce-fir forest of northeastern North America. The Maine Forest Service is responding to this outbreak with large spray projects, totalling 6.6 million acres in the past three years. It is also embarking on a program to develop an environmentally sound program of integrated management, relying heavily on silviculture, salvage, research, and improved insecticides.

Natural variation in balsam fir foliar components of dietary importance to spruce budworm

Year-to-year, geographical, and local variations in foliar concentrations of crude fat, nitrogen, total sugars, and starch and in foliar caloric value were determined for maturing, current-year needles of balsam fir (Abiesbalsamea L.). All except geographical variations proved to be statistically significant. Seasonal trends of chemical concentrations in maturing needles were in agreement with previous findings.Much of the variation in foliar caloric value could be explained by changes in foliar concentration of crude fat.Year-to-year changes in foliar nutrients may influence spruce budworm population dynamics.

MORPHOGENETIC EFFECTS OF AN INHIBITOR OF CUTICLE DEVELOPMENT ON THE SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE)

Abstract1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)-urea when ingested by the last two larval instars of the spruce budworm, Choristoneura fumiferana, inhibits cuticle development leading to morphogenetic deformities in the pupal stage. Laboratory and greenhouse studies indicate that this material could be used to control natural populations of spruce budworm.

AERIAL SPRAYING OF A BACILLUS THURINGIENSIS — CHITINASE FORMULATION FOR CONTROL OF THE SPRUCE BUDWORM (LEPIDOPTERA: TORTRICIDAE)

AbstractA 10,000 acre stand of mature balsam fir, in Temiscouata County, Quebec, which had a spruce budworm population of about 21 larvae/18 in. branch-tip was sprayed with a Bacillus thuringiensis + chitinase formulation. Aerial spraying was carried out by three TBM aircraft between 4 and 7 June 1972, when insect development was at the peak of the third instar. Where the quantity of B. thuringiensis colonies per square centimeter was higher than 77 and spray deposit higher than 0.4 gal/acre (U.S.), larval mortality was between 84% and 93% compared with between 39% and 53% in the check plot. Foliage protection was 47%. The results indicate the possibilities of using B. thuringiensis + chitinase to control spruce budworm infestations.

Frost reduces western spruce budworm populations and damage in Montana

Unseasonal temperatures, as low as −6°C, were recorded in western Montana in mid-June 1969, a period when western spruce budworm (Choristoneura occidentalis Freeman) larvae were actively feeding on newly developing foliage of coniferous host trees. Studies in progress at that time provided circumstantial evidence that the freeze reduced: (1) budworm populations on Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), western larch (Larix occidentalis Nutt.), and ponderosa pine (Pinus ponderosa Laws.) over 90%; and (2) budworm damage to young larch 54–71%.

Management of Spruce Budworm Populations

Management of Spruce Budworm Populations

Control of a Spruce Budworm Outbreak in Quebec through Aerial Spraying Operations

AbstractAn attempt was made to suppress an incipient spruce budworm outbreak in the Lower St. Lawrence region of Quebec through the aerial application of DDT. Operations began in 1960 and continued in 1961 and 1962 when they finally met with success. Failure to achieve success earlier was due partly to the exceptionally favourable survival conditions for the insect in 1960, and partly to the inadvertent omission of a small infested area from the program in 1961. The operations greatly reduced spruce budworm populations each year in the outbreak area, while the action of natural control factors, including parasites and predators increased. The collapse of the outbreak was the result of the combined effects of the chemical treatments and of natural control factors.

The Dynamics of Epidemic Spruce Budworm Populations

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A RECENT SPRUCE BUDWORM OUTBREAK IN THE LOWER ST. LAWRENCE AND GASPE PENINSULA WITH REFERENCE TO AERIAL SPRAYING OPERATIONS

The main topics discussed in this paper are: the progress of the spruce budworm outbreak in the Lower St. Lawrence - Gaspé regions from 1949 to 1956; the areas sprayed between 1954 and 1958; timing of spray application in relation to insect abundance and development; effects of treatment on spruce budworm populations and on defoliation of balsam fir; results of aerial defoliation surveys and egg surveys; estimated amounts of wood destroyed by the insect, and losses averted through spraying; the various natural control factors associated with the decline and the eventual collapse of the outbreak.

Spruce Budworm Parasite Investigations in the Lower St. Lawrence and Gaspé Regions of Quebec

A spruce budworm outbreak started in Quebec and adjoining parts of New Brunswick in 1949 and spread each year until by 1955 most balsam fir stands within an area of 32,000 square miles were attacked. Approximately 45 per cent of this area was in the Lower St. Lawrence and Gaspe regions of Quebec. In Quebec, important population reductions took place in various sectors of the outbreak area as a result of unfavourable weather conditions in 1956 and 1957 (Blais, 1958a, 1958b), and the final collapse occurred in 1958 when populations returned to the endemic level throughout the area (Blais and Martineau, 1958). In New Brunswick, a relatively small outbreak area remained at the end of the summer in 1958 (Webb et al., 1959). The large-scale aerial applications of DDT begun in New Brunswick in 1952, and in Quebec in 1954, were continued until 1958. Biological studies in connection with the spraying were carried out in both provinces. In Quebec these studies consisted of assessing spruce budworm population fluctuations in both sprayed and unsprayed areas and in determining, where possible, the causes for these fluctuations. All factors associated with changes in population could not be adequately measured over such a large territory, but a real attempt was made to obtain information on parasitism. The present paper deals with this aspect of the studies.