*******98********** Twospotted Spidermite [Ornamentals] (Tetranychus urticae)-Hort Answers - University of Illinois Extension
University of Illinois Extension

University of Illinois Extension

Hort Answers

Insect Relative Damage

Twospotted Spidermite [Ornamentals]
Tetranychus urticae

Spider mite web strand
Spider mite web strand
 
Frequency
5 (1 = rare 5 = annual)
 
Severity
4 (1 = very little damage 5 = plants killed)
 
Hosts
In addition to attacking azaleas and rhododendrons, this mite attacks many other woody plants as well as numerous herbaceous plants. It also attacks many house plants.

 
Plants Affected

Annual

Groundcover

Perennial

Shrub

Tree

 
Symptoms

This mite is green to greenish yellow with two dark spots on its back. This mite is also known as red spidermite; however, this mite is rarely red in the U.S. but is commonly red in Europe. Red mites on plants in the U.S. are usually predatory mites that are eating pest mites. Thin silk strands may be found due to mite infestation. Stippling,the tiny yellow to whitish spots due to feeding, may cause the leaves to die and turn brown when infestations are severe.

Particularly on house plants, this mite encloses attacked leaves in fine silk webbing. Outdoors, wind and rain typically wash the webbing away.

 
Life Cycle
The females overwinter in leaf litter or under the bark of several different trees and shrubs. Reproduction can occur throughout the growing season as long as the weather is warm enough. With its short generation time, it commonly has 20 or more generations per year. On house plants, these mites will reproduce throughout the year.

 
Management

Beneficial mites may be present at the same time as the twospotted spider mite. Plant feeding mites such as the twospotted spider mite move slowly and if crushed leave a greenish stain. Beneficial mites move fairly rapid and when crushed leave a reddish stain. Check for mites by vigorously shaking/tapping a branch onto a piece of white paper. Watch closely. The mites will move while the debris will not. Do not treat if beneficial mites are present since they are natural control for plant mites. Treat if only the plant mites are present.

Infestations can be controlled with 2 to 3 weekly sprays of insecticidal soap, summer spray oil, or chemical miticides.

 
Related Resources
Home, Yard & Garden Pest Guide
Illinois Commercial Landscape and Turfgrass Pest Management Handbook
U of IL - Distance Diagnosis through Digital Imaging
U of IL - Plant Clinic