OVERWINTERING MORTALITY OF SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA (CLEM.) (LEPIDOPTERA: TORTRICIDAE), POPULATIONS UNDER FIELD CONDITIONS

1998 ◽  
Vol 130 (1) ◽  
pp. 13-26 ◽  
Author(s):  
Jacques Régnière ◽  
Pierre Duval

AbstractOverwintering mortality in the spruce budworm, Choristoneura fumiferana (Clem.), was measured between 1983 and 1990 in several natural stands of balsam fir, Abies balsamea (L.), in Quebec and Ontario. Overwintering losses (disappearance of larvae) averaged 25.2%, occurred mostly in late summer and early fall, and were probably caused by, in large part, failure to spin a hibernaculum, diapause-free development, and invertebrate predation. An average of 24.1% of larvae were found dead in the hibernaculum. This mortality also occurred early in diapause and during post-diapause development, and overwintering mortality did not vary much from year to year. We conclude that overwintering mortality does not result from adverse winter weather conditions or from gradual loss of hibernacula. Overall overwintering mortality from the loss of hibernating larvae plus death within the hibernaculum averaged 43.2% and was not related to infection with the microsporidian Nosema fumiferanae (Thomson). We observed no influence of position in the tree crown on overwintering survival. There was a 40% decrease in overwintering survival among larvae from eggs laid very late in a female’s oviposition sequence. Survival within the hibernaculum on shoots of A. balsamea bearing different types of spinning substrates varied considerably, and was highly correlated with larval spinning preferences. Shoots bearing lichen mats, rough bark, male flower scars, or 1-year-old annular scales were most suitable, whereas shoots bearing annular scales older than 1 year or smooth bark were least suitable. The efficiency of the NaOH extraction technique to recover overwintering spruce budworm larvae was found to be highly variable, and to depend on population density, shoot type, and the proportion of live larvae on the branches.

2021 ◽  
Author(s):  
Skye Butterson ◽  
Amanda D Roe ◽  
Katie Elizabeth Marshall

High latitude insect populations must cope with extreme conditions, particularly cold temperatures. Insects use a variety of cold hardiness mechanisms to withstand this temperature stress, and these can drive geographic distributions through overwintering mortality. The degree of cold hardiness can be altered by two evolved responses: phenotypic plasticity and local adaptation. Phenotypic plasticity can occur within or between generations (transgenerational plasticity; TGP), and local adaptation can evolve through directional selection in response to regional climatic differences. We used the eastern spruce budworm, Choristoneura fumiferana (Lepidoptera: Tortricidae) as a model to explore the role that variable winter temperatures play in inducing two aspects of plasticity in cold hardiness: TGP and local adaptation in phenotypic plasticity. This species is one of the most destructive boreal forest pests in North America, therefore accurately predicting overwintering survival is essential for effective management. While we found no evidence of TGP in cold hardiness, there was a long-term fitness cost to larvae that experienced repeated cold exposures. We also found evidence of local adaptation in both seasonal and short-term plasticity of cold hardiness. These findings provide evidence for the importance of phenotypic plasticity and local adaptation when modelling species distributions.


2008 ◽  
Vol 25 (3) ◽  
pp. 139-145 ◽  
Author(s):  
Sarah L. Taylor ◽  
David A. MacLean

Abstract Aerial sketch mapping (ASM) of annual defoliation provides a means to quantify spruce budworm (Choristoneura fumiferana Clem.) outbreak histories, but accuracy is affected by factors such as navigation and weather conditions. We used ground-based defoliation estimates from 123 permanent sample plots (PSP) in New Brunswick and increment core growth data from a subset of PSPs, to validate ASM estimates of defoliation. From 1985 to 1993, 85% of 332 cases were correctly classified by aerial estimates as nil–light (0–30%) or moderate–severe (31–100%), with the proportion correct varying by measurement year, defoliation severity, and host species. Growth indices generated from 81 visually cross-dated and verified balsam fir (Abies balsamea [L.] Mill.) tree-ring series in 23 PSPs were significantly negatively correlated with aerial-derived cumulative defoliation for 87% of the PSPs, and correlation increased when aerial estimates were combined with ground survey data. We conclude that aerial surveys provide a reasonable estimate of defoliation history to estimate growth reduction.


1961 ◽  
Vol 93 (2) ◽  
pp. 118-123 ◽  
Author(s):  
J. G. Pilon ◽  
J. R. Blais

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.


1986 ◽  
Vol 62 (2) ◽  
pp. 96-100 ◽  
Author(s):  
D. J. McRae

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.


1977 ◽  
Vol 109 (9) ◽  
pp. 1239-1248 ◽  
Author(s):  
O. N. Morris

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.


1996 ◽  
Vol 128 (6) ◽  
pp. 1109-1113 ◽  
Author(s):  
Harald Piene

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.


1983 ◽  
Vol 59 (6) ◽  
pp. 294-297 ◽  
Author(s):  
J. R. Blais

Forest managers have expressed the need for guidelines that would predict, up to 5 years, the annual spruce budworm damage on a stand basis. Reasons why reliable prediction is generally not possible are discussed. It is suggested that long-term management programs, that would take into consideration periodic losses resulting from recurring budworm outbreaks and that would be based on regional differences in the vulnerability of fir-spruce stands, should be implemented. Key words: Spruce budworm, Choristoneura fumiferana; forest management; tree mortality; defoliation; stand vulnerability, balsam fir, Abies balsamea.


2011 ◽  
Vol 41 (5) ◽  
pp. 1112-1120 ◽  
Author(s):  
Sergio Rossi ◽  
Hubert Morin

The renewal of balsam fir (Abies balsamea (L.) P. Mill.) stands is related to the recurrent spruce budworm (Archips fumiferana Clemens [syn.: Choristoneura fumiferana (Clemens)]) outbreaks that favour the growth of the regeneration following death of the dominant trees. The aim of this study was to investigate the population demography and the spatial relationships among individuals in four permanent plots of the boreal forest of Quebec, Canada, after a spruce budworm outbreak. This was realized by collecting data on trees and saplings every five years from 1994 to 2004 and by using Ripley’s K statistics. The younger plots showed recruitment of up to 90 new trees·ha–1·year–1, and mortality following competition among individuals affected up to 27% and 50% of the trees and saplings, respectively. In the plot with the lowest tree density, sapling recruitment was estimated as 378 new individuals·ha–1·year–1. Saplings were aggregated at all spatial scales, whereas trees showed a random pattern of stem distribution. A significant tendency to separation between saplings and trees was observed. The specific stand dynamics observed in balsam fir are connected to an abundant advance regeneration and an age-dependent competition for resources in a heterogeneous environment with different levels of resource availability.


1972 ◽  
Vol 104 (7) ◽  
pp. 1051-1054
Author(s):  
J. F. Stewart ◽  
N. R. Brown

AbstractA series of low-volume spray treatments were conducted to study the contact and residual effect of two concentrations of the insecticide phosphamidon to fourth instar spruce budworm, Choristoneura fumiferana (Clem.), on balsam fir, Abies balsamea (L.) Mill, and red spruce, Picea rubens Sarg. Treatment of sprayed larvae on sprayed trees, unsprayed larvae on sprayed trees, and sprayed larvae on unsprayed trees, resulted in two principal conclusions: (a) Higher concentrations of phosphamidon (1% versus 0.5% active) accelerated mortality in all instances and (b) no statistical difference (P = 0.1%) was found in the final mortalities between treatments in which only the foliage was treated and where both larvae and foliage were treated with phosphamidon.


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