The oak moth's larvae can consume entire leaves.
The majestic oak tree can suffer defoliation by the moth larvae of the California oak tree moth (Namus scientificensis). A native insect of the coastal regions of California, the moth's caterpillars cause widespread leaf damage to the area's native oak trees. The larvae will also feed lightly on other deciduous trees. Does this Spark an idea?
Appearance and Occurrence
Outbreaks of the oak moth occur in 8- to 10-year cycles. The outbreaks usually persist for one to two years. The adult moths appear tan or off-white. Each one measures approximately 1 inch in length. The males sport feathered antennae. Two to three generations occur per year from March to November. Homeowners often notice the adults hovering around oak trees in the late afternoon. The female moth lays her eggs on the oak tree to provide an ample food source for the hatching larvae. The adult moth does not feed on the oak tree.
Caterpillars
The oak moth caterpillar grows up to 1 inch in length before pupating into an adult. The body of the oak moth caterpillar has a light fur covering. The caterpillar has a greenish color with a black or dark brown head. The caterpillars produce silk, which they use to suspend themselves from the tree's foliage. When disturbed, the caterpillars will suddenly drop from the tree's foliage and swing from their attached silken line. Homeowners often notice silken masses of caterpillar on trees, fence posts or mailboxes.
Damage
A hardy tree, the oak can withstand defoliation by the caterpillars if it is in a healthy condition. Trees already suffering from stress from drought or other factors may succumb to the insect. The pests skeletonize the tree's leaves, and as they grow, they will consume entire leaves with ease. Damaged leaves will turn brown and fall from the tree. Entire neighborhoods and oak forests can suffer complete defoliation during the years when the oak moth population burgeons, according to the University of California.
Control
The oak moth caterpillars usually do not warrant control because the tree will eventually recover from the insect's damage. An already weak or sick tree may benefit from the application of an insecticide early in the season to control the moth's larvae. Beneficial parasitic flies often help to reduce the population of the oak moth caterpillars. Maintain a healthy oak tree that can withstand the insects onslaught by regular watering, pruning and fertilizing. Avoid injuring the tree through over cultivation or by using a lawnmower across any of the tree's exposed roots.
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