TWOSPOTTED SPIDER MITE

James R. Baker & S. Bambara, Extension Entomologists

General Information

Twospotted spider mites can be rusty green, greenish amber or yellow and unlike insects, have eight legs instead of six. Overwintering females are red or orange. These mites have two (sometimes four) black spots on top. They are very small, but still visible.

The eggs vary from transparent and colorless to opaque straw yellow. The first stage larva is colorless to pale green or yellow and has only six legs. Nymphs are similar to adults except in size. Nymphs are pale-green to brownish-green and have eight legs. Large spots of black may develop on each side.

Biology

Twospotted spider mites are widely distributed in the United States and feed on over 180 host plants, including over 100 cultivated species. Violets, chickweed, pokeweed, wild mustard and blackberry are common sources from which mites spread to nearby plants. Twospotted spider mites pierce the epidermis of the host plant leaf with their sharp, slender mouthparts. When they extract the sap, the mesophyll tissue of the leaf collapses in the area of the puncture. Soon a chlorotic spot forms at each feeding site. After a heavy attack, an entire plant may become yellowed, bronzed or killed completely. The mites may spin so much webbing over the plant that it becomes entirely covered.

Twospotted spider mites occur as important pests on more crops than any insect pest in the Southeast. Though insects and mites are in a group called the Arthropoda (meaning jointed foot), because jointed legs are common to both, spider mites are not actually insects. They are more closely related to spiders and derive their name from the thin web that some species spin.

In the Southeast, twospotted spider mites overwinter as adults in the soil or on weed hosts such as violets. Roses, daylilies, hollyhock, marigold and other herbaceous flowers are common hosts in the garden. In mild winter weather, twospotted spider mites continue to feed and lay eggs, although development in the winter is much slower than in the summer. Six-legged larvae hatch from the eggs. They develop into eight-legged nymphs, which pass through two nymphal stages. After each larval and nymphal stage, there is a resting stage. The adults mate soon after emerging from the last resting stage, and in warm weather the females soon lay eggs. Each female may lay over 100 eggs in her life and up to 19 eggs per day. Development is most rapid during hot, dry weather. A single generation may require as many as 20 or as few as 5 days to reach adulthood before it begins producing offspring.

Control

For chemical management use one of the following pesticides according to label. Practice pesticide class rotation to reduce resistance.

See NC Pesticide Manual for more choices.
*Suitable for home use.

Other Resources

• Back to Insect Notes
• Horticulture Information Leaflets(HILs)
• Plant Disease Notes
• North Carolina Agricultural Chemicals Manual
• North Carolina Cooperative Extension Service

Published by North Carolina Cooperative Extension Service

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.

ENT/ort-25
April 1994 (Revised) May 1997

Web page last reviewed January, 2008 by the webperson.