Spruce Budworm: Early Response
Strategy
Spruce budworm is the most destructive insect
eating its way through North American softwood forests. For quite
some time, researchers at the Laurentian Forestry Centre of the Canadian
Forest Service have been studying this pest, looking for ways to limit
damage to our forests. They now propose a new method for fighting
spruce budworm. The current spruce
budworm control strategy is aimed at protecting foliage (keeping
defoliation levels under 50%) so that trees stay alive through an
epidemic. The use of Bacillus thuringiensis (B.t.),
a biological insecticide, has been limited to dense, commercially
valuable balsam fir stands.
Spruce budworm caterpillar.
Photo: T. Arcand
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This approach has certain inherent weaknesses:
if the moths are migrating at a high rate, the outbreak may get
out of control; and if defoliation exceeds 50%, the most vulnerable
conifers (fir, spruce) will stop growing and hard-hit, untreated
stands then become sources of infestation.
Forest attacked by spruce budworm.
Photo: P. Therrien
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An early response strategy would solve these problems.
The objective of this new approach is to limit the reach of spruce
budworm populations at the local level (rather than control defoliation
in specific stands) through successive applications of B.t.
from the very outset of an epidemic.
There may be considerable advantages to this approach:
- With defoliation levels kept under 20%, tree growth
would be unaffected;
- The growth rate and severity of the epidemic would
be reduced because B.t. would be applied throughout a region,
regardless of the commercial value of the stands treated;
- The epidemic might be shorter because pest
populations would be reduced by natural enemies which would have
a greater impact in the treated sector (see box).
Progress of a Spruce Budworm Epidemic.
Spruce budworm populations decline
as soon as they enter the overlap area, where the rate of
mortality caused by natural enemies is high enough to have
a lasting effect. |
The abundance of natural enemies and the seriousness
of epidemics are directly related to stand composition and density;
implementing the strategy would therefore create new knowledge about
the role stand management can play in preventing spruce budworm
epidemics.
CFS-LFC researchers work in collaboration with several
partners:
- Société de protection des forêts
contre les insectes et maladies (SOPFIM)
- Quebec’s Ministère des Ressources
naturelles, de la Faune et des Parcs (MRNFP)
- Université Laval
- Carleton University (Ottawa)
- Forest Protection Ltd. (New Brunswick)
- Provincial governments of Ontario and Manitoba
For further information, please
contact:
Jacques Régnière
Natural Resources Canada, Canadian Forest Service
Laurentian Forestry Centre
1055 du P.E.P.S., P.O. Box 3800, Sainte-Foy, Quebec G1V 4C7
Phone: (418) 648-5257 • Fax: (418) 648-5849
E-mail:
Web site: www.cfl.cfs.nrcan.gc.ca
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© Her Majesty the Queen in Right of Canada 2003
Catalogue Number Fo29-54/6-2003E
ISBN 0-662-34021-3
ISSN 1705-5784
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