California Oakworm Description:
The California oakworm is a caterpillar species that feed on oak trees throughout California. The larva is about 1-inch long with yellow/green bodies and black stripes down either side and a light orange/brown head. Adult moths are small with tan/gray wings.
Damage is most common on coast live oaks, but all oak trees are susceptible. Infestation levels are unpredictable and vary from year to year.
California Oakworm Life Cycle:
Female moths lay a few dozen eggs on the underside of leaves. When the larvae hatch, they feed on the entire leaf, often leaving it skeletonized or destroying the leaf entirely. There are two generations per year.
During active seasons, inspect your oak trees regularly for signs of oakworms. Look for skeletonized or mostly chewed foliage. The caterpillars drop dark frass pellets as they feed. Monitoring frass is another method for detecting damaging levels. Fertilizing trees that show extensive damage may be helpful. Insecticide applications may be needed to maintain tree aesthetics. Your local arborist can recommend the best treatment option for your property.