Predicting balsam fir mortality in boreal stands affected by spruce budworm

Nearly all forest regions in the Province of Quebec where balsam fir (Abies balsamea (L.) Mill.) is an important tree component have been subjected to severe defoliation by the spruce budworm, Choristoneura fumiferana (Clem.), during the past 20 years. These outbreaks have followed an easterly direction beginning near the Ontario-Quebec border in 1939 and ending in the Gaspé Peninsula in 1958.

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The influence of hardwood content on balsam fir defoliation by spruce budworm

Canadian Journal of Forest Research ◽

10.1139/x26-182 ◽

1996 ◽

Vol 26 (9) ◽

pp. 1620-1628 ◽

Cited By ~ 108

Author(s):

Qiong Su ◽

Ted D. Needham ◽

David A. MacLean

Keyword(s):

New Brunswick ◽

Natural Enemies ◽

Spruce Budworm ◽

Balsam Fir ◽

Generalized Model ◽

Stand Management ◽

Working Hypothesis ◽

Model Combining

Changing stand composition by increasing hardwood content has been suggested as a long-term method for reducing susceptibility and vulnerability of balsam fir (Abiesbalsamea (L.) Mill.) to spruce budworm (Choristoneurafumiferana (Clem.)). Twenty-five mixed balsam fir–hardwood stands were selected in northern New Brunswick, with five stands in each 20% hardwood class (0–20, 21–40%, etc.). Defoliation each year from 1989 to 1993 was significantly (p < 0.0001) related to hardwood content, with r2 ranging from 0.57 to 0.81. As hardwood content increased, defoliation of balsam fir decreased. From 1989 to 1992, the years of moderate to severe defoliation, balsam fir stands with <40% hardwoods sustained 58–71% defoliation, on average, versus 12–15% defoliation in stands with >80% hardwood. A generalized model combining hardwood content and the estimated defoliation in pure softwood stands in a given year explained 77% of the variation in defoliation over stands and years. This study indicated that mixed balsam fir–hardwood stand management, with hardwood content >40%, could substantially reduce losses during spruce budworm outbreaks. Further research is warranted to elucidate the mechanism involved, but our working hypothesis is that greater hardwood content increased the diversity or populations of natural enemies such as birds and parasitoids.

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Prescribed Burning for Stand Conversion in Budworm-killed Balsam Fir: An Ontario Case History

The Forestry Chronicle ◽

10.5558/tfc62096-2 ◽

1986 ◽

Vol 62 (2) ◽

pp. 96-100 ◽

Cited By ~ 1

Author(s):

D. J. McRae

Keyword(s):

Fuel Consumption ◽

Prescribed Burning ◽

Choristoneura Fumiferana ◽

Abies Balsamea ◽

Spruce Budworm ◽

Fire Spread ◽

Fire Effects ◽

Balsam Fir ◽

Prescribed Burn ◽

Stand Conversion

Recent spruce budworm (Choristoneura fumiferana [Clem.]) infestations have resulted in widespread areas of balsam fir (Abies balsamea [L.] Mill.) mortality in Ontario, and there is growing interest in reestablishing these areas quickly as productive forests. One technique being used is prescribed fire after a salvage and bulldozer tramping operation. A 445-ha prescribed burn was carried out under moderate fire danger conditions in northern Ontario. The site, which was covered by balsam fir fuel that had been killed by spruce budworm, was tramped to improve fire spread. Weather, fuel consumption, and fire effects are reported. The burn effectively reduced heavy surface fuel loadings and consequently planting on the site was easier. Key words: Prescribed burning, fire, spruce budworm. Choristoneura fumiferana, balsam fir, Abies balsamea, fuel consumption, site preparation, tramping, stand conversion.

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Metabolites toxic to spruce budworm from balsam fir needle endophytes

Mycological Research ◽

10.1016/s0953-7562(09)80939-8 ◽

1992 ◽

Vol 96 (4) ◽

pp. 281-286 ◽

Cited By ~ 71

Author(s):

Larry A. Calhoun ◽

John A. Findlay ◽

J. David Miller ◽

Norman J. Whitney

Keyword(s):

Spruce Budworm ◽

Balsam Fir

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LONG TERM STUDY OF THE EFFECTIVENESS OF AERIAL APPLICATION OF BACILLUS THURINGIENSIS – ACEPHATE COMBINATIONS AGAINST THE SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE)

The Canadian Entomologist ◽

10.4039/ent1091239-9 ◽

1977 ◽

Vol 109 (9) ◽

pp. 1239-1248 ◽

Cited By ~ 15

Author(s):

O. N. Morris

Keyword(s):

Bacillus Thuringiensis ◽

Choristoneura Fumiferana ◽

Larval Mortality ◽

Abies Balsamea ◽

Spruce Budworm ◽

White Spruce ◽

Balsam Fir ◽

Population Densities ◽

Long Term Study

AbstractBacillus thuringiensis (Dipel® 36B) mixed with a sublethal concentration of acephate (Orthene®) (O, S-dimethyl acetylphosphoramidothioate), an organophosphorous insecticide, was applied at 2.35–14 l./ha to white spruce (Picea glauca) and balsam fir (Abies balsamea) trees infested with spruce budworm, Choristoneura fumiferana (Clem.). The treatment rate was 20 Billion International Units of B. thuringiensis (B.t.) activity with or without 42 g of active ingredient of acephate/ha.The ground deposit of the standard Dipel wettable powder formulation was 12% of emitted volume compared with 21–32% for the Dipel 36B flowable. The viability of B.t. spores was drastically reduced after 1 day of weathering but a high level of biological activity by the spore–crystal complex persisted for up to 20 days post-spray due probably to crystal activity.The addition of about 10% of the recommended operational rate of acephate to the B.t. suspension increased larval mortality by 34% when applied at 4.7 l./ha. Reductions in budworm populations were 97–99% in B.t. + acephate plots and 86–90% in B.t. alone plots.Plots with moderate budworm densities of up to 27 larvae/100 buds on white spruce and 36/100 on balsam fir were satisfactorily protected from excessive defoliation in the year of spray by B.t. with or without acephate. Plots with higher population densities were not satisfactorily protected based on the branch sample examination but aerial color photographs indicated good protection to the top third of the trees. Population declines were greater and defoliation and oviposition were lower in the treated plots than in the untreated checks 1 year later without further treatment. Two years later the larval population densities in all plots were low but the density was twice as high in the untreated check as in the treated plots, indicating long term suppression by the treatments. Defoliation was negligible in all plots.The treatments had no deleterious effect on spruce budworm parasitism. The data indicate that the integrated approach using Bacillus thuringiensis – chemical pesticide combinations is a viable alternative to the use of chemical pesticides alone in spruce budworm control. Large scale testing is now warranted.

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

Canadian Journal of Forest Research ◽

10.1139/x77-007 ◽

1977 ◽

Vol 7 (1) ◽

pp. 47-53 ◽

Cited By ~ 9

Author(s):

G. G. Shaw ◽

C. H. A. Little

Keyword(s):

Population Dynamics ◽

Natural Variation ◽

Spruce Budworm ◽

Balsam Fir ◽

Total Sugars ◽

Caloric Value ◽

Seasonal Trends ◽

Geographical Variations ◽

Foliar Concentrations ◽

Foliar Concentration

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.

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CHANGES IN SPRUCE BUDWORM DEFOLIATION WITH CROWN LEVEL

The Canadian Entomologist ◽

10.4039/ent1281109-6 ◽

1996 ◽

Vol 128 (6) ◽

pp. 1109-1113 ◽

Cited By ~ 3

Author(s):

Harald Piene

Keyword(s):

Nova Scotia ◽

Choristoneura Fumiferana ◽

Abies Balsamea ◽

Spruce Budworm ◽

Cost Effective ◽

Balsam Fir ◽

Crown Length ◽

Cape Breton ◽

Cost Effective Approach ◽

The Common

AbstractDetailed estimates of defoliation caused by spruce budworm [Choristoneura fumiferana (Clem.)] over the crown length of young balsam fir [Abies balsamea (L.) Mill.] were made throughout a spruce budworm outbreak from 1976 to 1984 in the Cape Breton Highlands, Nova Scotia. The results show no clear tendency for a particular level of the crown to be damaged more heavily than any other. Thus, there is no reason to continue the common practice of taking samples from the mid-crown level on the assumption that they represent an ‘average’ level of defoliation either for high or low populations. Sampling from the bottom of the crown should provide a more convenient and cost-effective approach for estimating defoliation.

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Sample Sizes Required To Estimate Defoliation of Spruce and Balsam Fir Caused by Spruce Budworm Accurately

Northern Journal of Applied Forestry ◽

10.1093/njaf/15.3.135 ◽

1998 ◽

Vol 15 (3) ◽

pp. 135-140 ◽

Cited By ~ 7

Author(s):

David A. MacLean ◽

Wayne E. MacKinnon

Keyword(s):

Black Spruce ◽

Spruce Budworm ◽

Balsam Fir ◽

Sample Sizes ◽

Preliminary Assessment ◽

Travel Costs ◽

Host Trees ◽

Sampling Protocols ◽

Spruce Stands ◽

Number Of Branches

Abstract Data from the assessment of current defoliation levels on 172,000 individual shoots from 6890 midcrown branches sampled from balsam fir and spruce stands were used to define sampling protocols for assessing defoliation caused by spruce budworm. The method was based on sampling one midcrown branch from each of x host trees per stand, and assessing defoliation of y individual shoots per branch. Both the number of shoots per branch and the number of branches required per stand varied with host species (balsam fir, white spruce, or red-black spruce) and with average defoliation level. Sample sizes required to estimate mean defoliation with 90% confidence that the confidence interval is ±10% ranged from 7 to 24 branches per stand and from 17 to 58 shoots per branch, with the largest samples required at moderate (31-70%) defoliation levels. Estimated costs of shoot and branch sampling and processing ranged from $40-110/stand, based on a 90% confidence level salary rate of $12(Can.)/hr, and excluding travel costs. Results can be applied using a preliminary assessment to determine the general defoliation level, which along with species, determines the required sample size. North. J. Appl. For. 15(3):135-140.

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Spatial and temporal patterns of balsam fir mortality in spaced and unspaced stands caused by spruce budworm defoliation

Canadian Journal of Forest Research ◽

10.1139/x95-099 ◽

1995 ◽

Vol 25 (6) ◽

pp. 902-911 ◽

Cited By ~ 23

Author(s):

David A. MacLean ◽

Harald Piene

Keyword(s):

Temporal Patterns ◽

Spruce Budworm ◽

Balsam Fir ◽

Feeding Damage ◽

Spatial And Temporal Patterns ◽

Cape Breton Island ◽

Plot Size ◽

Cape Breton ◽

Significant Difference ◽

Percent Mortality

Spatial and temporal patterns of balsam fir (Abiesbalsamea (L.) Mill.) mortality were studied during a spruce budworm (Choristoneurafumiferana Clem.) outbreak from 1976 to 1984 on Cape Breton Island, Nova Scotia. Natural mortality in four insecticide-protected plots was 0% in spaced and 9–15% in unspaced stands, with only the smallest trees dying. Budworm-caused mortality (i.e., total minus natural) was 31–49% and 11–32% in spaced and unspaced young fir plots, respectively, but reached 94–100% in severely defoliated spaced plots, unprecedented in the literature for young fir mortality caused by the spruce budworm. Mortality began in the fourth to sixth year of defoliation, being earliest in the severely defoliated plots. From 80 to 90% of trees that died had > 75% cumulative defoliation, and most (64–100%) of the smallest (2 cm DBH) trees died. There was no significant difference in percent mortality between 25 spaced and 13 unspaced plots (p = 0.434), although, on average, mortality was 10–22% higher in the spaced plots. About 20–30% more of the intermediate-sized and largest trees were killed in the spaced plots. High spatial plot to plot variability in mortality occurred, which was apparently related to observed differences in the amount of defoliation and especially the incidence of "back-feeding" (damage to noncurrent foliage), as well as to plot size. Because budworm-caused mortality exhibits a distribution that tends to form large "holes" in stands, the degree of between-plot variability is related to plot size, and it is recommended that small plots that may miss these patches of mortality be avoided.

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