Quantification of Douglas-fir growth losses caused by western spruce budworm defoliation using stem analysis

1985 ◽  
Vol 15 (1) ◽  
pp. 5-9 ◽  
Author(s):  
R. I. Alfaro ◽  
A. J. Thomson ◽  
G. A. Van Sickle
Keyword(s):  
Tree Mortality ◽  
Spruce Budworm ◽  
Douglas Fir ◽  
Western Spruce Budworm ◽  
Potential Growth ◽  
Cross Sectional ◽  
Reduced Ring ◽  
Periodic Growth ◽  
Growth Loss ◽  
The Impact

Periodic growth and volume losses in Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees in one stand defoliated four times in their lifetime by western spruce budworm (Choristoneuraoccidentalis (Freeman)) are reported. Losses were calculated by comparing periodic growth for the years of reduced ring increment with potential growth estimated using the IMPACT growth loss program. Proportional losses in stem radius and cross-sectional area remained approximately constant or declined slightly from tree top to base; losses differed at all stem levels among the infestations. Average gross volume losses per tree relative to the potential volume the trees should have reached at the end of each loss period were 17, 15, 8, and 13% for the 1920's, 1940's, 1950's, and 1970's infestations, respectively. In the last infestation, losses ranged from 9% in trees defoliated from 1 to 50%, to 18% in trees defoliated 91–100%. Cumulative tree volume losses, calculated by adjusting growth during all loss periods to their potential values, were estimated to be 44% of the potential volume the trees should have reached by 1977 had the trees never been defoliated. On a per hectare basis, the 1970's infestation in this stand caused an estimated 60 m3 (18%) loss, comprising 40 m3 (12%) owing to tree mortality and 20 m3 (6%) of growth deficit in the surviving trees.

Differential effects of Douglas-fir tussock moth and western spruce budworm defoliation on radial growth of grand fir and Douglas-fir

1979 ◽  
Vol 9 (1) ◽  
pp. 95-105 ◽  
Author(s):  
Linda B. Brubaker ◽  
Shannon K. Greene
Keyword(s):  
Host Species ◽  
Radial Growth ◽  
Ring Width ◽  
Spruce Budworm ◽  
Douglas Fir ◽  
Western Spruce Budworm ◽  
Tussock Moth ◽  
Rate Of Growth ◽  
Growth Loss ◽  
The Impact

This study compares the effects of separate Douglas-fir tussock moth (Orgiapseudotsugata McDunnough) and western spruce budworm (Choristoneuraoccidentalis Freeman) infestations on the radial growth of two host species, grand fir (Abiesgrandis (Doug.) Lindl.) and Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco). Growth records from nonhost species were also examined to substantiate that growth reduction in the hosts resulted from feeding by the respective defoliators. Ring-width data, standardized to remove trends of decreasing width from pith to bark, were tested statistically to identify significant differences in the effects of each defoliator on each host species. Four measures of radial growth were examined: maximum rate of growth decline, average rate of growth recovery, 1-year growth loss, and 5-year growth loss. The effects of tussock moth did not differ statistically between host species, but the impact of budworm defoliation on grand fir was significantly greater than on Douglas-fir. Differences occurred between the overall effects of tussock moth and budworm on the host species, with tussock moth causing significantly more rapid growth reductions and greater growth losses than budworm. It is concluded that (1) grand fir and Douglas-fir ring patterns, individually or in combination, can provide good evidence of severe defoliation by Douglas-fir tussock moth, (2) grand fir ring patterns can be used to identify severe defoliation by western spruce budworm, and (3) Douglas-fir ring patterns can provide evidence of budworm infestation only if corroborative evidence of a budworm infestation is present in the ring patterns of grand fir trees in the same stand.

ESTIMATING NUMBER OF WESTERN SPRUCE BUDWORM EGGS FROM EGG MASS MEASUREMENTS IN BRITISH COLUMBIA

1982 ◽  
Vol 114 (7) ◽  
pp. 643-645 ◽  
Author(s):  
J. W. E. Harris ◽  
A. F. Dawson
Keyword(s):  
British Columbia ◽  
Extended Period ◽  
Spruce Budworm ◽  
Douglas Fir ◽  
Population Trends ◽  
Egg Mass ◽  
Western Spruce Budworm ◽  
Growth Loss ◽  
Insect Populations ◽  
The Relationship

Western spruce budworm, Choristoneura occidentalis Freeman, periodically attacks Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) in British Columbia, causing mortality, deformity, and growth loss. Insect populations are assessed annually by the Canadian Forestry Service's Forest Insect and Disease Survey, by branch sampling for egg mass densities; predictions of population trends and damage are based on these assessments. Eggs, laid in rows in masses affixed to needles, are a preferred stage to sample because they are easily collected, remain fixed in numbers for an extended period, and precede damage by sufficient time to plan suppression or other programs. Numbers of masses alone, however, may not show population trends accurately as egg numbers per mass varies. Thus it is sometimes necessary to count eggs (Miller 1957), which is a formidable task. Fortunately egg numbers can be estimated from the dimensions of egg masses (Washburn and Brickell 1973). In this study, we determined the relationship between egg numbers and egg mass length and number of rows for samples from Douglas-fir stands frequently affected by spruce budworm throughout British Columbia. Data were collected over 3 years, 1977-79, during which time budworm populations were in a period of decline.

Tree mortality and radial growth losses caused by the western spruce budworm in a Douglas-fir stand in British Columbia

1982 ◽  
Vol 12 (4) ◽  
pp. 780-787 ◽  
Author(s):  
R. I. Alfaro ◽  
G. A. Van Sickle ◽  
A. J. Thomson ◽  
E. Wegwitz
Keyword(s):  
Radial Growth ◽  
Tree Mortality ◽  
Small Diameter ◽  
Basal Area ◽  
Spruce Budworm ◽  
Douglas Fir ◽  
Radial Increment ◽  
Western Spruce Budworm ◽  
Number Of Stems ◽  
The Relationship

The effects of defoliation by western spruce budworm (Choristoneuraoccidentalis (Freeman)), on Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) radial growth at breast height and tree mortality are given. Four hundred and twenty trees were marked in an 81-year-old stand, and their defoliation levels were recorded annually from 1970 to 1980 in an outbreak that lasted from 1970 to 1974, inclusive. Forty-one trees were felled and dissected in 1977, 3 years after recovery began. The number of stems per hectare was reduced by 39.3% and basal area by 11.6% through mortality, most occurring among the small diameter, suppressed, and intermediate trees. Relationships were established between mortality and defoliation. Radial increments were examined, and the presence of four outbreaks during the life of the stand was detected. The combined effect of these infestations amounted to a loss of about 12% of the estimated potential diameter had not the insects been active. The most recent outbreak (1970–1974) caused a total of 10 years of subnormal growth, including 5 years due to defoliation and 5 years of recovery. The relationship between radial increment losses and defoliation intensity and duration is studied and quantified.

Western Spruce Budworm Damage to Sprayed and Unsprayed Young Douglas-Fir

1988 ◽  
Vol 3 (2) ◽  
pp. 44-46 ◽  
Author(s):  
Rene I. Alfaro ◽  
Emil Wegwitz
Keyword(s):  
British Columbia ◽  
Regression Model ◽  
Pseudotsuga Menziesii ◽  
Tree Mortality ◽  
Spruce Budworm ◽  
Douglas Fir ◽  
Choristoneura Occidentalis ◽  
Western Spruce Budworm

Abstract Defoliation, mortality, and top-kill were measured in 40-year-old, open-grown Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) under attack by the western spruce budworm (Choristoneura occidentalis [Freeman]) in the interior of British Columbia, in control trees and trees treated with ground sprays of the insecticide Sevin. In untreated trees that sustained repeated defoliation of 50 to 90% of the total crown foliage, tree mortality began after four years and had reached 29% after eight years. Thirty-four percent of the survivors in this group suffered top-kill, which averaged 1.0 m at the end of eight years. No mortality and only negligible top-kill occurred in trees, sprayed or not, which sustained less than 50% defoliation. A regression model of the probability of tree mortality based on the defoliation is presented. West. J. Appl. For. 3(2):44-46, April 1988.

RELATIONSHIPS BETWEEN ATTACK RATES AND SURVIVAL OF WESTERN SPRUCE BUDWORM, CHORISTONEURA OCCIDENTALIS FREEMAN (LEPIDOPTERA: TORTRICIDAE), AND BUD DEVELOPMENT OF DOUGLAS-FIR, PSEUDOTSUGA MENZIESII (MIRB.) FRANCO

1992 ◽  
Vol 124 (2) ◽  
pp. 347-358 ◽  
Author(s):  
Roy F. Shepherd
Keyword(s):  
Close Association ◽  
Spruce Budworm ◽  
Larval Survival ◽  
Douglas Fir ◽  
Choristoneura Occidentalis ◽  
Western Spruce Budworm ◽  
Bud Development ◽  
Feeding Sites ◽  
Vegetative Buds ◽  
Wide Range

AbstractIndividual larvae of western spruce budworm (Choristoneura occidentalis Freeman) were observed from overwintering emergence to pupation at six locations spread over a wide range of altitudes and thus climate. A weekly census of 100 lower-crown buds per plot indicated large differences in rates of bud development and larval survival among locations.Emerging second-instar larvae attempted to mine swelling buds of Douglas-fir. If the buds were hard and tight, larvae mined 1-year-old needles until penetrable buds were available. Larvae dispersed over the crowns with only one larva becoming established in each bud; thus, many early-emerging and surplus larvae could not find suitable feeding sites and disappeared. Within the protective bud, survival was high. After buds flushed and larvae became exposed, densities dropped, probably due to increased predation and decreased food quality. Correlations indicated a close association between larval survival for the exposed period between bud flush and pupation, and overall larval survival.Douglas-fir trees responded to initial bud removal, but not to needle removal, by inducing latent buds in the axils of needles to grow into active vegetative buds ready to develop and flush the next spring. The number of these new vegetative buds formed was greatest when the initial buds were removed early in the season before flush, and decreased thereafter. Trees with vigorous crowns had the greatest response to defoliation by inducing the largest number of latent buds into becoming active vegetative buds; these were found mainly on the 2- and 3-year-old internodes.

INFLUENCE OF FOLIAR NITROGEN LEVELS ON SURVIVAL, DEVELOPMENT, AND REPRODUCTION OF WESTERN SPRUCE BUDWORM, CHORISTONEURA OCCIDENTALS (LEPIDOPTERA: TORTRICIDAE)

1985 ◽  
Vol 117 (1) ◽  
pp. 23-32 ◽  
Author(s):  
J. Wayne Brewer ◽  
John L. Capinera ◽  
Robert E. Deshon ◽  
Mary L. Walmsley
Keyword(s):  
Larval Mortality ◽  
Spruce Budworm ◽  
Dry Weight ◽  
Douglas Fir ◽  
Nitrogen Level ◽  
Pupal Weight ◽  
Western Spruce Budworm ◽  
Foliar Nitrogen ◽  
Nitrogen Levels ◽  
White Fir

AbstractThe influence of nitrogen levels in foliage of white-fir, Abies concolor, and Douglas-fir, Pseudotsuga menziesii, seedlings on various biological characteristics of the western spruce budworm, Choristoneura occidentalis Freeman, was studied. Seedlings were grown under greenhouse conditions and provided with nutrient solutions to maintain five foliar nitrogen levels ranging from 1.29 to 4.42% dry weight for white fir and 1.43 to 3.94% for Douglas fir. Larvae confined to treated seedlings were monitored through the next generation. Larval mortality was higher, and development time longer, at both upper and lower extremes of foliar nitrogen than at mid-level. Mean pupal weight was significantly greater for larvae reared on white fir with the mid-range foliar-nitrogen level. Mean number, and weight, of eggs laid were highest when larvae fed on foliage from the mid-range nitrogen level. Total number of larvae produced was lowest at the high and low extremes of foliar nitrogen levels.

Balancing risks of disturbance from mountain pine beetle and western spruce budworm

2009 ◽  
Vol 39 (4) ◽  
pp. 839-848 ◽  
Author(s):  
V.G. Nealis ◽  
M.K. Noseworthy ◽  
R. Turnquist ◽  
V.R. Waring
Keyword(s):  
Pinus Contorta ◽  
Mountain Pine Beetle ◽  
Lodgepole Pine ◽  
Spruce Budworm ◽  
Douglas Fir ◽  
Closed Field ◽  
Western Spruce Budworm ◽  
Mountain Pine ◽  
Pine Beetle ◽  
Population Processes

The effect of removing lodgepole pine ( Pinus contorta Dougl. ex Loud.) and retaining Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) to reduce the risk of disturbance from mountain pine beetle ( Dendroctonus ponderosae Hopk.) in mixed conifer stands in southern British Columbia, Canada, on population processes influencing outbreaks of western spruce budworm ( Choristoneura occidentalis Free.) was evaluated in 10 paired (open vs. closed) field plots. Overall feeding damage to Douglas-fir was significantly, but only slightly, lower in open stands compared with closed stands. Although open plots tended to recruit more budworms, the losses resulting from the dispersal of spring-emerging budworms in search of feeding sites were significantly greater in open plots. The forest management benefits of these early season losses were mitigated, however, by more mortality of budworms from natural enemies, particularly diseases, in the closed plots during the budworm feeding period. These results are discussed in terms of compensating population processes and balancing objectives in forest pest management. In this case, selective harvesting of lodgepole pine as a mitigation strategy for the mountain pine beetle conserved the midterm timber supply potential represented by associated Douglas-fir even in the presence of an outbreak of the western spruce budworm.

Stochastic simulation of growth loss in thinned balsam fir stands defoliated by the spruce budworm in Newfoundland

1998 ◽  
Vol 28 (5) ◽  
pp. 703-710 ◽  
Author(s):  
Erhard John Dobesberger
Keyword(s):  
Stochastic Simulation ◽  
Larval Density ◽  
Abies Balsamea ◽  
Spruce Budworm ◽  
Damage Function ◽  
Balsam Fir ◽  
Negative Exponential Function ◽  
Attack Pattern ◽  
Growth Loss ◽  
The Impact

A stochastic simulation model was developed to derive a damage function for the spruce budworm, Choristoneura fumiferana Clem. (Lepidoptera: Tortricidae), and balsam fir, Abies balsamea (L.) Mill., herbivore interaction at the stand level for open-grown trees. Both aggregated and uniform models of attack pattern by late-instar larvae based on k of the negative binomial were evaluated to determine the impact of larval density and attack pattern on the loss in stemwood volume increment of young, thinned balsam fir stands in Newfoundland. Percentage loss in stemwood increment was a nonlinear, negative exponential function of initial larval density. Implementation of control measures to prevent 50% defoliation that is caused by about 14 larvae/branch tip would result in saving 24% of the annual stemwood increment after 1 year of defoliation and about 32% after 2 years of cumulative defoliation. Aggregation of spruce budworm larvae among trees within a forest stand results in less growth loss compared with a uniform pattern of attack. The nonlinear damage function may suggest tolerance and possibly compensatory growth after herbivory by low population levels of the spruce budworm.

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