Oak Trees – Attack Of The Caterpillars

Q: We have an infestation of caterpillars in our oak trees. Their droppings are covering our deck and driveway. Should we spray or just wait it out? 

A: You have a big population of orange-striped oak worms. These caterpillars are basically a ‘stomach with legs’ so leaves disappear rapidly during the weeks they feed. The caterpillars are two to three inches long with yellow-orange stripes running the length of their body. Because oak worms ingest such tremendous amounts of food one of the ways they are discovered is through the thickly scattered waste pellets that fall from a tree’s foliage. On a quiet day, the pellets can be heard clattering down through the leaves and hitting the ground below. These fall caterpillars are the offspring of a moth who laid her eggs on the tree several weeks ago. Fortunately, poisons are rarely needed. Mother Nature provides a lifespan of only a few weeks before the caterpillar drops to the ground and pupates. Usually, there is only one generation per year. Since oak trees lose their leaves naturally in the fall even complete defoliation does little harm.