Plant Problem Diagnosis Key / Pests
Pest
Spider mites
Tetranychus urticae and relatives
Eight-legged mites about 1/50 inch long that feed on leaf cells from below. Heavy populations spin silk over tips and flowers. Populations build fastest in hot, dry air.
Signs
- Fine white or yellow stipple on the upper leaf surface; leaves look bronzed or bleached when feeding is heavy.
- Moving specks under the leaf, often with two dark spots.
- Tap a leaf over white paper: specks that crawl are mites; specks that stay are dust.
What favors it
Hot, dry air (low humidity, high VPD), water stress, and long-lasting sprays that kill their predators.
Prevention
- Check plants every 3-5 days in hot, dry weather.
- Keep plants watered and humidity in range; mites build fastest in hot, dry air.
- Release predatory mites before numbers build, at the first sign of stipple.
Often confused with
Sources
- Twospotted spider mites in home gardensUniversity of Minnesota Extension
- Two-Spotted Spider Mite (Tetranychus urticae)Montana State University Extension
- Two Spotted Spider Mites on High Tunnel VegetablesUniversity of Maryland Extension
Treatment by crop
Cultural, biological and chemical options in the order to use them, and notes written for each crop.
Identification is free. Treatment is on the Home and Pro plans.
Questions in the key that lead here
- Look the plant over, leaf undersides included. Are insects, mites, slugs, eggs, webbing or droppings on it?
Yes, something living or its traces - What is on the plant?
Specks that are hard to see by eye - What does the damage look like?
Fine pale dots (stippling) on the upper leaf, maybe silk webbing
Not a match? Start the key or describe what you see.
More photos
More from university Extension: search Extension pages on spider mites, or find a plant diagnostic lab through your state's Extension.
Other pests
- Aphids
- Bagworms
- Bark beetles of pine and spruce
- Broad mites and cyclamen mites
- Caterpillars
- Cicada and twig-cutting damage
- Colorado potato beetle
- Cucumber beetles
- Cutworms
- Elm leaf beetle
- Emerald ash borer
- Flea beetles
- Fungus gnats
- Galls on leaves and twigs
- Hemlock woolly adelgid
- Japanese beetles
- Lace bugs
- Leafminers
- Mealybugs
- Pine sawflies
- Root aphids
- Root-knot nematodes
- Russet mites
- Sapsucker damage
- Scale insects
- Shore flies
- Slugs and snails
- Spongy moth (gypsy moth)
- Spotted lanternfly
- Squash bugs and stink bugs
- Squash vine borer
- Tent caterpillars and fall webworm
- Thrips
- Whiteflies
- Wood borers