''Choristoneura freemani'', the western spruce budworm, is a species of
moth
Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...
of the family
Tortricidae
The Tortricidae are a family of moths, commonly known as tortrix moths or leafroller moths, in the order Lepidoptera. This large family has over 11,000 species described, and is the sole member of the superfamily Tortricoidea, although the genu ...
. It is the most destructive defoliator of coniferous forests in western North America.
Distribution
It is now widely distributed throughout the
Rocky
''Rocky'' is a 1976 American sports drama film directed by John G. Avildsen and written by and starring Sylvester Stallone. It is the first installment in the ''Rocky'' franchise and stars Talia Shire, Burt Young, Carl Weathers, and Burgess M ...
and
Coast Mountains
The Coast Mountains (french: La chaîne Côtière) are a major mountain range in the Pacific Coast Ranges of western North America, extending from southwestern Yukon through the Alaska Panhandle and virtually all of the Coast of British Columbia ...
. The first recorded outbreak was in 1909 on the southeastern part of
Vancouver Island
Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian Provinces and territories of Canada, province of British Columbia. The island is in length, in width at its widest point, and in total area, while are o ...
in
British Columbia
British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
, Canada. Since that year, infestations have frequently been reported in western Canada.
[Fellin, D. and J. Dewey (March 1992)]
Western Spruce Budworm
Forest Insect & Disease Leaflet 53, U.S. Forest Service. Retrieved on: September 14, 2008.
The budworm was first recorded in 1914 in the United States, in
Oregon
Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...
. However, it was not initially recognized as a serious threat to coniferous forests in the western U.S. Aerial spraying apparently terminated some smaller epidemics in the southern and central Rockies; others subsided naturally. The insect then appeared to be dormant in US forests until 1922, when two outbreaks were reported near
Priest Lake
Priest Lake is a lake in Idaho, United States, in the northernmost portion of the Idaho Panhandle, 80 miles northeast of Spokane, Washington. The northern end of the lake extending to within 15 miles (24 km) of the Canada–US border. The ...
in northern
Idaho
Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...
. Since then, significant outbreaks in the Rockies and in the
Pacific Northwest
The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...
have caused top-killing and serious economic losses in tree growth. Tree mortality from budworm can occur in regeneration, sapling, and pole-sized trees. Trees in mature stands severely defoliated by the western spruce budworm may become susceptible to bark beetles, which kill mature trees.
[
]
Impact
Considered the most destructive defoliator in British Columbia, sustained outbreaks of the western spruce budworm resulted in defoliation of over in the Fraser Canyon
The Fraser Canyon is a major landform of the Fraser River where it descends rapidly through narrow rock gorges in the Coast Mountains en route from the Interior Plateau of British Columbia to the Fraser Valley. Colloquially, the term "Fraser Ca ...
- Lillooet
Lillooet () is a district municipality in the Squamish-Lillooet region of southwestern British Columbia. The town is on the west shore of the Fraser River immediately north of the Seton River mouth. On BC Highway 99, the locality is by road abou ...
- Pemberton area from 1949-58. From 1970 -2001 further outbreaks occurred over a much larger area including the area of the previous outbreaks, as well as the Thompson
Thompson may refer to:
People
* Thompson (surname)
* Thompson M. Scoon (1888–1953), New York politician
Places Australia
*Thompson Beach, South Australia, a locality
Bulgaria
* Thompson, Bulgaria, a village in Sofia Province
Canada
* ...
and South Okanagan
South Okanagan was a provincial electoral district in the Canadian province of British Columbia beginning with the 1916 British Columbia general election, election of 1916. Following the 1975 British Columbia general election, 1975 election bound ...
areas in 1970-2001.[Natural Resources Canada]
Western spruce budworm
. Conifer Defoliating Insects of British Columbia. Canadian Forestry Service. Retrieved on: September 14, 2008.
There is no typical pattern for western spruce budworm epidemics. Most of the early epidemics subsided naturally after a few years. Others persisted longer, but without spreading over large areas. An epidemic which began in 1949 in the northern Rocky Mountains has persisted for over 30 years despite insecticidal treatment of more than between 1952 and 1966.[
]
Description
232px, Western spruce budworm caterpillar, sixth (final) ">instar
Adult moths are about 1/2 inch (12.7 mm) long and have a wing-spread of 7/8 to 11/8 inches (22 to 28mm). Moths of both sexes are similar in appearance, although the females are a bit more robust than males. Both sexes fly. The gray- or orange-brown forewings are banded or streaked, and each usually has a conspicuous white dot on the wing margin. Eggs are oval, light green, and about 3/64 inch (1.2mm) long and overlap like shingles.
Larvae develop through six stages. Newly hatched larvae are yellow-green with brown heads. In the next three stages, larvae have black heads and collars and orange- or cinnamon-brown bodies. In the fifth stage, larvae have reddish-brown heads marked with black triangles, black collars, and pale olive-brown bodies marked with small whitish spots. Mature larvae are 1 to 11/4 inches (25 to 32 mm) long, with tan or light chestnut-brown heads and collars and olive- or reddish-brown bodies with large ivory-colored areas.
Pupae are 1/2 to 5/8 inch (13 to 16 mm) long, broad at the head end, and narrower toward the tail. They are brownish yellow or brownish green at first, and later turn reddish brown.
Life cycle
Throughout most of its range, the western spruce budworm completes one cycle of development from egg to adult within 12 months. Moths emerge from pupal cases usually in late July or early August; in the southern Rockies, adults often begin emerging in early July.
The adults mate, and within 7 to 10 days, the female deposits her eggs and then dies. Each female deposits approximately 150 eggs, usually on the underside of conifer needles. Eggs are laid in one to three-row masses containing a few to 130 eggs, with an average of 25 to 40 eggs per mass.
Larvae hatch from eggs in about 10 days. Larvae do not feed, but seek sheltered places under bark scales or in and among lichens on the tree bole or limbs. Here, they spin silken tents in which they remain inactive through the winter.
In early May to late June, larvae leave their hibernacula to search for food. They first mine or tunnel into year-old needles, closed buds, or newly developing vegetative or reproductive buds.
New foliage, which is normally the preferred food, is usually entirely consumed or destroyed before larvae will feed on older needles. Larvae become full grown usually in early July about 30 to 40 days after leaving their overwintering sites.
Larvae pupate in webs of silk they have spun either at the last feeding site or elsewhere on the tree. The pupal stage usually lasts about 10 days.
Taxonomy
The species was originally named '' Choristoneura occidentalis'' by Freeman. However, this name was already in use for an African species described by Walsingham. The replacement name for this North American species is ''Choristoneura freemani''.
References
{{Taxonbar, from=Q17153399
Moths described in 2008
Moths described in 1967
Choristoneura