Pest description and damage The adult moth is yellowish to dark brown. Mature larvae of the western oak looper are about one-inch long and light brown with black spots when mature. They move in a characteristic "looping," inchworm fashion. The western oak looper feeds mainly on the foliage of the Oregon white (or Garry) oak (Quercus garryana). It is probably the most damaging insect on white oak from Oregon north to British Columbia. In some years, oaks over large areas in the Willamette Valley are defoliated. The damage is temporary, since the trees leaf out the next year, and outbreaks are not sustained.
See Table 2 in: