Webspinning Spider Mites

The twospotted spider mite is most common in the Sacramento Valley and the Pacific spider mite in the San Joaquin Valley. Both species produce abundant webbing on both sides of the leaves. The two mites are not easily distinguished. Both have two black spots on their yellow green bodies. In fall they turn orange red. The twospotted spider mite and Pacific spider mite overwinter as adult females under bark and in weeds. When weeds dry in spring, the mites move to trees and feed on lower leaves first. There are many overlapping generations each summer, with eggs being laid on the underleaf surface.

Spider mites feed by sucking the contents out of leaf cells. Such leaf damage reduces tree vitality. Most feeding takes place on the underside of leaves. Heavy feeding causes browning of leaves and defoliation.

Vigorously growing trees are much more tolerant to mite attack than trees under stress. Maintain trees with optimum irrigation and fertilization. Reducing dust not only reduces spider mite populations but also may limit Alternaria rot disease.

Predaceous mites, Metaseiulus spp., and the sixspotted thrips, Scolothrips sexmaculatus, feed heavily on webspinning mites and may give complete control in the orchard. The western flower thrips, Frankliniella occidentalis, feeds on mite eggs and may prevent a mite population from increasing.

No economic threshold levels have been established for spider mites on figs. Apply treatments before leaf damage becomes severe and defoliation from mite damage ensues.