Choristoneura conflictana, the large aspen tortrix, is a tortricid native to North America. The undergoes periodic that can severely defoliate trembling aspen stands in parts of Manitoba and Saskatchewan. are active from May through August, with a wingspan of 25–35 mm. The species was first described by Francis Walker in 1863 and ranges across the continent from Alaska to the Atlantic coast.

Identification

are difficult to distinguish from related Choristoneura based on external alone; examination of genitalia is typically required for definitive identification. The species belongs to the 'fumiferana species group' within the . Larval leaf-rolling on aspen, poplar, willow, or alder may provide a field clue, but this behavior is shared with other tortricid species.

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Habitat

Associated with stands of trembling aspen (Populus tremuloides) and other broad-leaved trees including poplar, willow, and alder. Field studies have been conducted in northern Manitoba and Saskatchewan at various levels.

Distribution

Transcontinental in North America: from the Pacific coast to the Atlantic coast, and from Alaska south to California, Arizona, and New Mexico. Canadian records include Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland, Ontario, Quebec, Saskatchewan, and Yukon. US records include Alaska, Arizona, Arkansas, California, Colorado, Iowa, Kansas, Maine, Michigan, Minnesota, Missouri, Montana, Nebraska, New Mexico, New York, North Dakota, South Dakota, Utah, Wisconsin, and Wyoming.

Seasonality

on wing from May to August. Larvae overwinter and resume feeding in spring; older instars roll leaves for shelter.

Diet

Larval diet consists primarily of trembling aspen (Populus tremuloides). Laboratory studies confirm that quaking aspen is essential for increase. Larvae have also been observed feeding on poplar, willow, and alder. feeding habits not documented.

Host Associations

  • Populus tremuloides - primary larval Essential for increase; optimal for larval survival and
  • Populus spp. - larval Other poplar besides trembling aspen
  • Salix spp. - larval Willow
  • Alnus spp. - larval Alder

Life Cycle

Larvae overwinter and resume feeding in spring. Older instars roll leaves tightly around themselves as shelter from and . occurs within or near the leaf roll. occurs from May through August. Laboratory studies demonstrate that larval plant quality directly affects pupal weight and adult potential.

Behavior

Larvae construct tight leaf rolls for protection during later instars. are attracted to light and have been documented at blacklight stations. Periodic occur, with levels varying dramatically between years.

Ecological Role

Defoliator of trembling aspen; periodic can severely impact aspen stands. to at least 24 of in interior Alaska, including various and flies. Subject to , with a species-specific virus widespread in Ontario .

Human Relevance

Economic impact through defoliation of trembling aspen, a commercially important tree in Canada. Periodic in Manitoba and Saskatchewan have prompted ecological study. The species is reared in laboratory settings using modified McMorran diet for research purposes.

Similar Taxa

  • Choristoneura fumiferanaSpruce budworm; similar and highly variable coloration. Distinguished by association (conifers versus broad-leaved trees) and geographic overlap in some regions.
  • Other Choristoneura speciesMembers of the 'fumiferana group' share highly variable coloration; reliable separation requires genitalia examination or molecular methods.

More Details

Population Dynamics

The exhibits dramatic fluctuations, with periodic causing severe defoliation. Field studies from 1950–1954 in northern Manitoba and Saskatchewan documented variable population levels, but specific drivers of outbreak cycles remain incompletely characterized.

Natural Enemies

Twenty-four documented from interior Alaska , indicating substantial top-down pressure. An specific to C. conflictana is widespread in Ontario and also infects C. fumiferana.

Laboratory Rearing

Successfully reared on modified McMorran artificial diet, enabling research without live plants. This has facilitated studies on host plant effects on and .

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