Sap-Sucking Insects, Gall Formers and Mites
FIELD GUIDE TO INSECTS AND DISEASES OF ARIZONA AND NEW MEXICO FORESTS
Spider Mites
Oligonychus spp.

Hosts:  Conifers and hardwoods

Figure 81. Figure 81. Adult spider mites.

Symptoms/Signs:  Spider mites suck plant juices with needle like mouthparts, which cause spotting, yellowing, fading, and premature drop of foliage. When populations are heavy, cast skins, webbed foliage, eggs, and other mite activity can be found. Adult spider mites are tiny greenish to reddish colored arachnids with black heads.

Biology:  There can be several generations per year. Spider mites have five stages and all but the egg stage bear legs.

Figure 82. Figure 82. Damage to juniper caused by spider mites.

Effects:  Spider mites are mainly an ornamental tree problem and often go unnoticed in forested situations. Outbreaks of spider mites generally last 1 year and are kept under control by natural enemies, such as predatory mites.

Similar Insects and Diseases:  Aphid feeding can have the same symptoms of yellowing, spotting or fading foliage. Adult aphids have winged and wingless individuals. In general, aphids are larger in size and have three pairs of legs instead of four.

Leaf injury from compounds such as ozone may have similar symptoms such as yellowing, spotting, or fading.

References:  24, 46