Following severe infestations, leaves become discolored, producing an unthrifty gray or bronze look to the plant. Leaves and needles may ultimately become scorched and drop prematurely. Spider mites frequently kill plants or cause serious stress to them. Spider mites are small and often difficult to see with the unaided eye. Their colors range from red and brown to yellow and green, depending on the species of spider mite and seasonal changes in their appearance.
Many spider mites produce webbing, particularly when they occur in high populations.
This webbing gives the mites and their eggs some protection from natural enemies and environmental fluctuations. Webbing produced by spiders, as well as fluff produced by cottonwoods, often is confused with the webbing of spider mites. The twospotted spider mite is also the most important species on house plants. It is a prolific producer of webbing. Other mites may affect shade trees such as elm, mountain ash and oak.