Defoliating Insects

Several different types of insects eat oak leaves.  During defoliator outbreaks, caterpillars (larvae) may or may not be visible on the leaves, but the leaves will typically have a chewed appearance and possibly distorted growth.  Depending on the species involved, webbing may be visible, and the larvae may dangle from the tree on a silken thread.   During heavy infestations, trees may appear to bare or nearly so, and dying.  Most or all of the trees in an area may be affected.  However, defoliator outbreaks, even heavy ones, seldom kill oak trees.  The trees usually grow back a new set of leaves.  Locally common species that defoliate oaks include the western oak looper (Lambdina fiscellaria)and fruit tree leafroller (Archips argyrospila), but other species occur locally too.

Oak defoliator larvae      Oak Defoliate entire tree

More information on oak foliar feeders (see pp 14-26  in A Field Guide to Insects and Diseases of California Oaks)