Oakleaf Caterpillars Stripping Trees in Saline Co.
I’ve received many calls about oak trees being stripped of their leaves and piles of droppings being found around the same trees. The cause of this in most cases has been the Variable Oakleaf Caterpillar (Lochmaeus (Heterocampa)ß manteo). This native species occurs throughout the area and has come out in great numbers this fall. These caterpillars will attack all species of oaks and some other deciduous trees. The size of the tree does not matter and can range from saplings to large, mature trees.
The Variable Oakleaf Caterpillar goes through distinct stages in its life cycle:
Larval Stage:
Tiny spotted larvae start by feeding together near their hatched eggshells on the lower leaf surface, usually skeletonizing one to three leaves in a cluster. After their first molt, they feed individually, consuming entire portions of the leaf. They pass through five growth stages before dropping to the soil to pupate. Larvae in the last stage account for about 85 percent of defoliation. When disturbed, larvae secrete formic acid for defense, and prolonged handling may cause blisters Mature larvae are approximately 1.5” long and can be green, deep pink, or reddish. They have a dark red dorsal band, green heads with black vertical lines, and yellowish lateral lines along their bodies. Larvae in the last stage account for about 85 percent of defoliation. When disturbed, larvae secrete formic acid for defense, and prolonged handling may cause blisters.
Larvae stop feeding in early September, drop to the ground, and spin their cocoons.
Pupal Stage:
Mature larvae drop to the ground after they finish feeding, usually in late August or September. They burrow into the soil under leaf litter, creating a loose silk-lined cell. In this stage, they become inactive larvae (prepupae) throughout the winter. Pupation typically occurs in the soil cell in late May or June of the following year. Some individuals remain prepupae for an extended period, pupating in the second spring after defoliation. Pupae are about 0.75” long, light chestnut brown, smooth, and shiny.
Moth Emergence:
In the North, moths start emerging in late June and continue through late July. Females lay clusters of 30 to 300 eggs on the lower surface of host leaves, with each female laying up to 500 eggs.
The eggs hatch in 5 to 7 days. In the South, some moths emerge in midapril or early May, with eggs present by the end of April. Larvae hatch in May, feed until late June or early July, and pupate
in leaf litter cocoons. Adult moths appear in late July, and the secondgeneration larvae start feeding in mid-august. They move to the ground in September and pupate, overwintering as prepupae to pupate the following April.
After heavy infestation years there tends to be a drop off due to parasites attacking the caterpillar
eggs and larvae. Along with other predators such as other insects there may be a 90% drop in populations following a year of heavy defoliation.
Overall, the biggest issues with the Variable Oakleaf Caterpillar is the defoliation of trees and the droppings that are produced. Many homeowners have reported that the droppings are
the biggest nuisance. Fortunately, the droppings are not harmful to people or pets. Most trees can handle the defoliation that occurs from the pests feeding on leaves unless the infestation happens for over 2 years in a row. Sometimes a multi-year infestation can impair the tree vigor and growth. There isn’t much that can be done to control the caterpillars, especially when infestations are this widespread. The best thing to do is to monitor trees to make sure they don’t have any ill effects from the defoliation during hot summer days.
If you have any questions or concerns about your trees, please contact the Saline County Extension Office.