Oak skeletonizer complaints

Another popular bug that showed up recently to annoy folks is the oak skeletonizer, Bucculatrix ainsliella (Lepidoptera: Lyonetiidae).

The oak skeletonizer is a native insect that occurs throughout the Great Lakes region. The larval stages feed on the leaves of several species of oak. These tiny insects become a nuisance and terribly annoying when the larvae hang from the trees on silken threads and when they spin their cocoons on buildings, lawn furniture, stationary vehicles, kitchen appliances and other items that we might have occasion to store in or use to decorate our landscapes. At this point, there is not much that can be done.

The term “skeletonizer” refers to the manner in which the larvae feed on the leaves; they eat the leaf tissue, but leave the veins, giving the leaf a somewhat scaby appearance. Rarely is the feeding injury cause for alarm in Michigan. They do not bite people or pets. They do not attack or become established in dwellings.

There are two generations per year in Michigan. Most of the leaf feeding and annoyance problems we see are caused by the second generation in late August through September. They spend the winter months in small, white cocoons resembling ribbed grains of rice. The cocoons may be attached to fallen leaves, branches and limbs, or nearby structures. Unfortunately, little can done except washing or scraping them off. Spraying trees to control the caterpillars may help, but this can be very expensive when large trees are involved. In the spring, tiny little moths emerge and lay eggs on leaves where the larvae feed until they move off the host to pupate and begin the cycle again.

Cocoon
Two oak skeletonizer cocoons. The cocoons
are about 3/8 of inch long.
Photo credit: Kable Thurlow, MSUE

Hatched pupil case
Photo of an oak skeletonizer cocoon with
the hatched pupal case (left) hanging
underneath. Photo credit: Kable Thurlow, MSUE

Caterpillar
Here is what an oak skeletonizer caterpillar
looks like on a oak leaf.
Photo credit: G. Keith Douce, University of Georgia, forestry images.org.

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