This is one of a handful of insects - the others being the moths Operophtera brumata and Malacosoma californicum and the gall wasp Neuroterus saltatorius - that cause severe damage to Garry Oak trees, and at the time of writing (2001) C. trichostola is probably the most devastating of them all. The leaves of the Garry Oaks are almost completely skeletonized over our entire area. Ornamental non-native oaks seems to escape the damage.