The Birch Skeletonizer, Bucculatrix Canadensisella Chambers

Significant infestations can result in premature leaf drop. Periodic outbreaks of large populations are known to occur in various regions of its distribution.

The birch skeletonizer has one generation per year. Pupae overwinter in leaf litter, and the larvae are active in mid-summer. Caterpillars go through several developmental stages, as do the young of other insects. These developmental stages of immature insects are called "instars." The first instars of the birch skeletonizer caterpillars are leaf miners, feeding internally between the leaves' upper and lower surfaces. This feeding creates splotchy areas on the leaves that may initially be mistaken for pathogen infection. Leaf mines on birch leaves can also be caused by a sawfly, the birch leafminer, Fenusa pusilla (Lepeletier).

The older caterpillar instars feed on the undersurface of the leaf. The caterpillars molt twice to the next instar using silken mats they create on the leaf. These small white spots easily identify the presence of the skeletonizer. At the end of the caterpillar stage of their life cycle, they drop to the ground and form silken cocoons for overwintering. The cocoons may be attached to leaves and other ground debris. The pupae are very tolerant of fall and winter weather conditions. Warm and wet environments provide optimum conditions for hatching.

While the birch skeletonizer is most likely a minor pest and can usually be ignored, its feeding has resulted in significant defoliation in some areas. Unfortunately, defoliation occurs after the insect has finished immature development and is in the pupal stage. It is important to recognize that drought conditions, several other insect infestations, and fungal diseases also contribute to leaf drop in birches. It is essential to determine the cause of the leaf drop to address the issue appropriately.

Good cultural practices help manage the birch skeletonizer on valuable landscape birch trees. Cleaning up, removing, and destroying the leaf litter and debris below ornamental trees will reduce the number of pupae and lessen re-infestation for the following year.