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.

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.

scholarly journals Characterization of western spruce budworm outbreak regions in the British Columbia Interior

2018 ◽  
Vol 48 (7) ◽  
pp. 783-802 ◽  
Author(s):  
Lorraine E. Maclauchlan ◽  
Lori D. Daniels ◽  
Janice C. Hodge ◽  
Julie E. Brooks
Keyword(s):  
British Columbia ◽  
Spruce Budworm ◽  
Growth Suppression ◽  
Douglas Fir ◽  
Western North America ◽  
Western Spruce Budworm ◽  
The North ◽  
South Central ◽  
Ecosystem Classification

The western spruce budworm (WSB; Choristoneura freemani Razowski) shapes Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests throughout western North America with periodic, severe landscape-level defoliation events. The largest and most continuous recorded defoliation occurred in the 2000s, largely centered in the Williams Lake and 100 Mile House WSB outbreak regions, peaking in 2007 at 847 000 ha defoliated in British Columbia (B.C.). Unique WSB outbreak regions in south-central B.C. are described using biogeoclimatic ecosystem classification, geography, 106 years of documented defoliation, and 46 stand-level Douglas-fir host tree-ring chronologies. Since the 1980s, recorded defoliation in B.C. has shifted from coastal ecosystems and become a dominant disturbance in drier, colder, interior Douglas-fir ecosystems. Defoliation records demarcate four outbreaks from 1950–2012 and up to three growth suppression events from 1937–2012. Outbreak duration was shorter in the north and far south of B.C., with recovery periods (no trees showing growth suppression) shorter over all WSB outbreak regions in the 2000s, suggesting that trees may be increasingly susceptible to each successive defoliation event. Knowing the regional outbreak periodicity may facilitate early detection of incipient WSB populations, which is critical for management as many of our low-elevation Douglas-fir forests become more stressed with changing and unpredictable climate regimes.

Multicentury history of western spruce budworm outbreaks in interior Douglas-fir forests near Kamloops, British Columbia

2006 ◽  
Vol 36 (7) ◽  
pp. 1758-1769 ◽  
Author(s):  
Rochelle Campbell ◽  
Dan J Smith ◽  
André Arsenault
Keyword(s):  
British Columbia ◽  
Pinus Ponderosa ◽  
Ponderosa Pine ◽  
Survival Rates ◽  
Spruce Budworm ◽  
Douglas Fir ◽  
Western Spruce Budworm ◽  
Air Temperatures ◽  
Forest Sites ◽  
History Of

Western spruce budworm (Choristoneura occidentalis Freeman) is a native defoliator of forests in the interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) forests of British Columbia, Canada. Dendrochronological techniques and the software program OUTBREAK were used to reconstruct a defoliation history of Douglas-fir for 19 forest sites near Kamloops in central British Columbia. By comparing the radial-growth response of ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws.) with that of Douglas-fir growing in nearby but separate stands, eight western spruce budworm outbreaks over the past 300 years were distinguished. Although there is considerable variation in the timing and duration of these western spruce budworm events at the stand level, synchronous outbreaks have occurred in approximately 30- to 43-year cycles. Spectral analyses of a composite time series from all stands showed similar and consistent intervals between outbreaks. Climatic variation appears to have been important to budworm outbreaks in the 20th century. Notable outbreaks tended to occur during years with average spring air temperatures following winters with less than average precipitation. Based on this finding, it is proposed that with high over-winter survival rates and a longer growing season, the duration of outbreaks may increase in the future.

RELATING WEATHER TO OUTBREAKS OF WESTERN SPRUCE BUDWORM, CHORISTONEURA OCCIDENTALIS (LEPIDOPTERA: TORTRICIDAE), IN BRITISH COLUMBIA

1984 ◽  
Vol 116 (3) ◽  
pp. 375-381 ◽  
Author(s):  
A. J. Thomson ◽  
R. F. Shepherd ◽  
J. W. E. Harris ◽  
R. H. Silversides
Keyword(s):  
British Columbia ◽  
Spruce Budworm ◽  
Western Spruce Budworm ◽  
Forest Insect ◽  
Outbreak Area ◽  
Larval Emergence ◽  
Weather Parameters ◽  
Relationship Of ◽  
The Relationship

AbstractThe relationship of western spruce budworm outbreaks and population collapse to weather parameters was examined using long term weather records from two stations in the budworm outbreak area of British Columbia and outbreak patterns obtained from Forest Insect and Disease Survey records and from tree stem analyses.Outbreaks were associated with warm dry summers in conjunction with synchrony of larval emergence and bud flush. Collapse of the last two outbreaks was clearly associated with extreme high temperatures following moth flight. Collapse of the earlier outbreaks may have been due to asynchrony between larval emergence and bud flush.

Douglas-fir height growth affected by western spruce budworm

1983 ◽  
Vol 13 (3) ◽  
pp. 445-450 ◽  
Author(s):  
G. A. Van Sickle ◽  
R.I. Alfaro ◽  
A.J. Thomson
Keyword(s):  
British Columbia ◽  
Recovery Period ◽  
Spruce Budworm ◽  
Site Index ◽  
Height Growth ◽  
Douglas Fir ◽  
Western Spruce Budworm ◽  
Total Height

Detailed dissections of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees repeatedly defoliated by the western spruce budworm (Choristoneuraoccidentalis (Freeman)) in two areas of British Columbia indicated that budworm severely affected height growth. Dissected trees lost an average 7.3 internodes in each infestation, of which 4.2 were destroyed or failed to grow during the budworm feeding and recovery periods, and 3.1 were existing internodes lost to dieback. An average of one internode of subnormal size, produced during the recovery period, was also present. Total height was reduced by 32% (11.4 m) and 19% (5.9 m) in areas that sustained four and two infestations respectively. Budworm infestations lead to an underestimation of the site index for Douglas-fir in the affected areas.

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.

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