Pest description and damage These mites are small (0.01 inch in length), deep red, small, short-legged mite generally flattened in shape. These mites are at the base of needles, often in considerable numbers. They are on yew but also may occur on other evergreens.
Biology and life history Most mite species share a similar life cycle. The majority of species overwinter as eggs on host plants, although some may overwinter as adult females. Mites become active in the spring. There may be eight to ten overlapping generations per year.
Pest monitoring Observe the leaves for mites and webbing and check for the number of pest and predator mites. Sufficient biological control is achieved by midsummer.
Phytoseiid predator mites always keep mites under control if broad-spectrum insecticide applications are avoided. Insect predators of mites include lady beetle adults and larvae, thrips, and pirate bugs. Heavy rain and cold weather also suppress mite numbers.
Elimination of broadleaf weeds such as mallow, bindweed, white clover, and knotweed with cultivation or grasses may reduce mite numbers. Wash mites from the tree with a strong stream of water. This also dislodges dust and dirt, which favor an increase in mite numbers. Water trees properly, as drought-stressed trees are more susceptible. Avoid excessive nitrogen applications, as this encourages mites.
See Table 1 in: