Spider Mites infect many types of evergreen and deciduous trees as well as ornamental plants, roses, and azaleas. They are really not insects but are arachnids with eight legs, not six. Spider mites pierce and suck their way through leaves and needles and cause extensive damage to infested plants and trees. They are very tiny, yellow-orange creatures with two characteristic dark spots on either side of their bodies. Each of these mites may be less than 1 mm and are almost microscopic. They lay transparent round eggs.
Symptoms: These include dried withered leaves, yellow spots, and discoloration which can look like the effects of drought stress. Spider mites are usually present on the underside of leaves. It may be necessary to shake a leaf over a sheet of white paper to see them.
More information: University of Minnesota Extension