The Black-headed Budworm in Eastern Canada

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Abstract
The black-headed budworm, Acleris variana (Fern.), is a forest pest native to North America. Periodic outbreaks have been recorded since the late 1920's in eastern Canada, where the preferred host is balsam fir. An outbreak generally causes 2 years of severe defoliation but no tree mortality and only a slight loss in radial increment.Color patterns and measurements of the immature stages are given and limited data on age-interval survival rates are discussed. A key-factor analysis of 17 years’ data shows that population release is associated with years of low parasitism and favorable weather, while population decline is largely determined by late larval parasitism.