Webspinning Spider Mites

Twospotted spider mite eggs are laid on the undersides of leaves and are spherical, clear, and colorless when laid but become pearly white as hatch approaches. Nymphs, adult males, and reproductive adult females are oval shaped and generally yellow or greenish in color. There are one or more dark spots on each side of their bodies, and the top of the abdomen is free of spots. Adult female twospotted spider mites may cease to reproduce during the coldest winter months in production areas of colder inland valleys. Diapause is indicated by a change in color to bright orange.

Carmine spider mite, a close relative of the twospotted spider mite, is bright red in color. It is commonly found at low densities in southern California and San Joaquin Valley growing regions. Populations usually decline as temperatures warm in spring.

Spider mites can cause leaves to yellow and eventually die and drop from the plant. Loss of leaf surface reduces energy available to maturing fruit. Entire plants in heavily infested areas of the field may be defoliated. These mites also produce webbing on plants where they feed. Damage frequently occurs in 'hot spots' such as areas of the field near dusty roads.

Monitor fields weekly from June through August. Look for plants with yellowish leaves or defoliated plants. Examine plant leaves for webbing, especially on older leaves in the middle of the plant with symptoms. For spring-planted fields that are pruned in early July, treat after pruning for better coverage.

Predaceous mites are not as effective in controlling pest mites in crops such as eggplant with hairy leaves.