At Koby Pest Control, we provide fast and accurate pest identification by looking for conditions and environments that attract tree bugs and flying pests. Koby specializes in developing and implementing pest management plans including maintenance programs to prevent re-infestation and ensure the health of your trees.
In El Dorado County, oak trees are a part of life. They provide beauty to our environment and much needed shade during the hot summer months. They also provide an excellent food source for oakworms, sometimes known as leafrollers. These persistent pests can cause extensive damage to your beautiful trees.
In the warmer central valley and foothills of northern California, oakworms (Archips argyrospila) are the most common defoliator of oaks. The adult is a tan to gray moth with prominent veins in their wings.
The female lays about 2-3 dozen tiny round eggs on leaves or twigs. The eggs start off as white but become pinkish to brownish gray prior to hatching. The larvae are about ½ to 3/4 inches in length and are light green with black heads.
They commonly drop to the ground from oak trees on silken threads, wriggling vigorously when disturbed. Most folks realize they have an oakworm problem when they walk into the silken threads which can become numerous, annoying, and messy.
Young larvae skeletonize the leaf surface, while older larvae chew all the way through the leaf. Defoliation on live oaks may become extensive in May or June and again in July through September. Healthy trees can tolerate some damage; but trees under stress from drought or other factors may decline if defoliated.
The oakworm larvae excrete droppings (frass) that fall to the ground, deck, patio, or pool beneath the tree. As larvae grow, fecal pellets increase in size. Greater numbers of pellets are produced as the number of larvae increase or if the temperature rises, which causes caterpillars to feed faster.
Oaks tolerate feeding by moderate populations of oakworms, and control may not be needed when damage is low. Healthy and well-cared-for oaks can tolerate extensive defoliation without serious harm. If trees need protection from defoliation because they are stressed or of high aesthetic value, spraying of leaves and branches will control oakworm larvae and alleviate the damage they cause, also protecting the health of the tree. Control of the larvae will also reduce the fecal material and webbing that drops from the tree.