Mite feeding turns leaves brown (referred to as bronzing). Severe infestations can reduce overwintering carbohydrate levels, cause trees to defoliate and stunt young tree growth. In years of drought or high temperatures, tree susceptibility to mite damage is heightened. Leaves on the right show bronzing from mite feeding.
This information was developed from A Pocket Guide for IPM Scouting in Stone Fruits by David Epstein, Larry J. Gut, Alan L. Jones and Kimberly Maxson-Stein. Purchase this in a pocket-sized guide for reference in the orchard from MSU Extension (publication E-2840).