Oak Trees & Caterpillars

California tent caterpillar infestations usually end by midsummer.

Caterpillars frequently invade oak trees and cause damage by building unsightly tents, eating oak leaves and causing leaf loss. The type of caterpillar infestation varies depending upon geographic region.

Types

Oak trees in California are susceptible to the California tent caterpillar, while oaks in Illinois are attacked by yellownecked caterpillars. Gulf Coast states such as Alabama have a range of stinging varieties, including the hag moth caterpillar and the puss caterpillar. Oak trees in East Coast states such as New York harbor eastern and forest tent caterpillars.

Effects

California tent caterpillars and yellownecked caterpillars eat new leaves by the hundreds, causing extensive defoliation. The hag moth and puss caterpillars also feed on foliage; both varieties sting, but the puss caterpillar's venom is especially painful. Eastern caterpillars build silken tents in the spring, while forest caterpillars spin haphazard mats from branch to branch. Both species cause the loss of leaves and branches.

Prevention/Solution

A biological insecticide containing a bacteria called Bacillus thuringiensis controls many leaf-feeding and needle-feeding caterpillar populations. This bacteria works by paralyzing the caterpillars' digestive systems. It sickens and kills the insects but is harmless to humans.

References

• University of California Agriculture and Natural Resources: Caterpillar Pests of Oak Trees
• University of Illinois Extension: Yellownecked Caterpillar
• Auburn University Department of Entomology: Stinging Caterpillars - A Guide to Recognition of Species Found on Alabama Trees
• State University of New York College of Environmental Science and Forestry: Tent Caterpillars
• Colorado State University Extension: Bacillus thuringiensis