Spider Mites

Spider mites (Family: Tetranychidae) are classed as a type of arachnid, relatives of insects that also includes spiders, ticks, daddy-longlegs and scorpions. They have four pairs of legs, no antennae and a single, oval body region. There are many species of spider mites; most have the ability to produce a fine silk webbing.

Spider mites are common pest problems on many plants in yards and gardens. Injury is caused as they feed, bruising the cells with their small, whiplike mouthparts and ingesting the sap. They frequently kill plants or cause serious stress to them.

Spider mites have tiny mouthparts modified for piercing individual plant cells and removing the contents. This results in tiny yellow or white speckles. When many of these feeding spots occur near each other, the foliage takes on a yellow or bronzed cast. Once the foliage of a plant becomes bronzed, it often drops prematurely.

Broad-spectrum insecticide treatments for other pests frequently cause mite outbreaks, so, if applying any pesticides, avoid these when possible.

spider mites
Spider mites are very tiny, less than 1/50 inch long when adults. Their colors range from red and brown to yellow and green, depending on the species of spider mite and seasonal changes in their appearance.

twospotted spider mites
Twospotted spider mites (Tetranychus urticae Koch).

stippling on leaves caused by twospotted spider mites
Twospotted spider mite damage on bean plant.

spruce spider mites
Spruce spider mites (Oligonychus ununguis Jacobi)

spruce spider mite damage
Spruce spider mite damage.

Click on images to view full-size

Identification and Control Information

[Photos, left to right: David Cappaert, Michigan State University, Bugwood.org; Frank Peairs, Colorado State University, Bugwood.org; Whitney Cranshaw, Colorado State University, Bugwood.org; Ward Strong, BC Ministry of Forests, Bugwood.org]