Insects and Mites
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Insects and Mites
Two-Spotted Spider Mite
Scientific name: Tetranychus urticae
Class: Arachnida
Family: Tetranychidae
Images
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Info
Biological Description
- Two-spotted spider mite is a mite and not an insect
- Adult: Minute (less than 0.02 inch); yellow-green; eight-legged; feeding stages have dark pigmented spots on either side of their oval bodies
- Female: Circular body shape; slightly larger than male
- Male: Body pointed at hind end; has longer legs than female
- Immature: Yellow-green; there are both 6- and 8-legged stages
- Eggs: Small (less than 0.01 inch in diameter); pale yellow-green; round; found on leaf surface or within webbing spun by adult.
- Although all stages are usually yellow-green, two-spotted spider mite can sometimes be orange to red in color.
Economic Importance
- Two-spotted spider mite is a pest of soybeans.
- Outbreaks:
- Significant damage only occurs during years in which soybean plants undergo severe moisture stress for several days.
Life Cycle
- Two-spotted spider mite overwinters as fertilized females in loose soil and plant debris.
- In spring overwintered females seek out growing plants on which they lay their eggs.
- Both males and females are produced throughout the season.
- Generations:
- There are multiple generations throughout the season.
- Mites reproduce fastest when weather is dry, humidity is low, and plants are stressed.
Damage/Symptoms
- Spider mites feed by penetrating plant tissues with stylets (needle-like feeding parts) and removing cell contents.
- Remaining cell material coagulates to form an amber mass
- Plant water loss through leaves is increased in leaves damaged by mite feeding. Leaves then bronze, dry out, and drop from the plant.
- Leaf damage and loss reduces the soybeans' photosynthetic capacity, in turn reducing it's grain filling capacity.
- Infestations usually start at field edges where mites move in from adjacent grasses and weeds.
- Damage first appears as white flecks on the undersides of leaves. This condition is called "stippling."
- Under heavy infestations, plants may be completely covered with webbing.
- When mites colonize an new area, they transport themselves by spinning strands of silk that get caught in the wind. This process is called "ballooning."
Scouting Procedure and Economic Threshold
- Treatment is suggested if several leaves have active colonies and damage prior to the R6.5-7.0 stages.
- Re-examine the field four to five days after spraying to see if re-treatment will be necessary.
Excerpts from Integrated Pest Management Program – University of Wisconsin-Extension, Cooperative Extension Service. Field Crop, Crop Scouting Manual. 2001
Site Links
Insect Images
Extension-Based Conference Proceedings
- Spider mites: A to Z. Cullen, E. 2006. pp. 130-133. In Proceedings 2006 Wisconsin Fertilizer, Aglime, and Pest Management Conference, University of Wisconsin, Madison, WI.
Wisconsin Crop Manager Articles
- Remember to scout for spider mites in soybeans for August. Wisconsin Crop Manager, Vol.14 No.22, August 2, 2007. Cullen, E.
- Potential for Two-Spotted Spider Mite Outbreaks Exists. Wisconsin Crop Manager Newsletter, Vol.13 No.20, July 20, 2006. Cullen, E.
- Spider mites - threshold overview, effects of rain. Wisconsin Crop Manager, Vol.12 No.21: 174. Jul. 28, 2005. Cullen, E.
PowerPoint
- Spider Mites: A to Z. Cullen, E. 2006.
Last updated:October 21, 2009
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