Picea: Spruce Spider Mite

Problem
Needles are stippled yellow and dirty. There may be a silken webbing on the twigs and needles. Needles usually turn brown and fall off. To determine if the tree is infested with mites, hold a sheet of white paper underneath some stippled needles and tap the foliage sharply. Minute dark green to black specks about the size of pepper grains will drop to the paper and begin to crawl around. The pests are easily seen against the white background.

Analysis
(Oligonychus ununguis)

The spruce spider mite is one of the most damaging pests of spruces and many other conifers. These mites suck sap from the undersides of the needles. As a result of feeding the green pigment disappears, causing the stippled appearance. This symptom may be mistaken for certain types of air pollution damage (see PAN). Spider mites first appear between April and June. In subtropical areas, mites may be active during warm periods in winter. A complete generation may be produced in only 17 days, so mites can rapidly build up to tremendous numbers during the growing season. Young spruce trees may die the first season. If left uncontrolled for several years, older trees may die, with symptoms progressing from the lower branches upward. Several other kinds of mites may infest spruce trees.

Solution
Spray with a miticide containing hexakis. Repeat the spray 2 more times, 7 to 10 days apart. Additional sprays may be needed in early fall or spring if the tree becomes reinfested.