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How to identify it
- To the naked eye they look like tiny moving dots; a 10X hand lens shows them clearly.[1]
- Adults have eight legs and an oval body with two red eyespots near the head. The twospotted spider mite has a large dark spot on each side, and the spots can spread to cover the body as it feeds.[1][4][2]
- Overwintering females turn orange or red and lose their spots. Colorado State says this color change may be why mites are sometimes called red spiders.[4][1][3]
- Silk webbing on infested leaves is the easiest way to tell spider mites from other mites and from aphids or thrips. It is heaviest in large infestations; spider webs and cottonwood fluff are sometimes mistaken for it.[1][3][2]
- Eggs are round and translucent, like tiny droplets, turning cream-colored before they hatch; NC State says they are clear to pale green and about 1/200 inch (0.14 mm) across. Empty egg shells stay on the leaf and help confirm a mite problem.[1][4][3]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Predatory mites | About the same size but with longer legs, a more teardrop shape and much faster movement; they eat spider mites and should be protected.[1][3] |
| Clover mite | A turfgrass mite that commonly wanders into homes in fall and spring. Webbing on leaves points to spider mites instead.[3][1] |
Where it lives
The twospotted spider mite is native to Eurasia and now established worldwide, a pest of outdoor and protected crops with a very broad host range. Dry conditions favor spider mites, one reason they matter so much in the more arid parts of the country, and indoors the twospotted spider mite is the most important mite on house plants.[4][5][6][3]
Biology and life cycle
Newly hatched larvae have six legs; the two nymph stages and adults have eight.[1][4]
In hot weather a generation can be completed in less than a week, and mites can be full-grown about a week after hatching.[1][3]
Mated females produce both male and female offspring; unmated females lay eggs that develop only into males. Generations overlap, so all life stages are usually present at once.[4]
In colder areas mated females overwinter under rough bark and in ground litter, then resume feeding and laying eggs in spring. In milder parts of California they can keep feeding all year on plants that stay green.[1][4][3]
Numbers usually build from June through September and often crash in late summer as predators catch up, the weather cools or rain falls. As leaves decline, females ride wind currents to new plants.[1]
Dry conditions favor spider mites: they feed more when humidity is low, most of their predators need moister air, and drought-stressed plants become more nutritious to them.[3][1]
Damage and signs
- Feeding first shows as fine pale stippling or flecking on leaves; leaves may then bronze, yellow or redden and drop.[1][3][2]
- Damage is worst in hot, dusty conditions and on water-stressed plants, and the symptoms can be mistaken for drought stress.[1][2]
- Leaf loss on squash, melons and other annual vegetables can cut yields and lead to sunburned fruit, and on beans and sugar peas they attack the pods. On ornamentals the damage is mostly cosmetic, though very high numbers can kill annual plants.[1]
- Hosts include blackberries, blueberries, strawberries, raspberries, currants, cucumbers, snap beans, peas, tomatoes, eggplant, lettuce, marigolds, New Guinea impatiens, arborvitae, azalea, spruce and roses; azaleas may develop distorted leaves and flowers.[2][3]
Health risk
Spider mites feed only on plants, piercing plant tissue to suck out cell contents; their harm is to leaves, flowers and fruit.[1][2][3]
Control
Prevention
Keep plants well watered, which Minnesota puts at about one inch of water a week for most plants, and don't fertilize during drought. Dusty conditions often lead to outbreaks, so water dusty paths and areas regularly and hose dust off plants.[1][2][3]
Traps and physical control
Spray the undersides of leaves forcefully with water; on gardens and small fruit trees this often keeps numbers low. It also washes away webbing and dust that shelter the mites from predators.[1][2][3]
On house plants, treat every susceptible plant at the same time: trim and bag heavily infested leaves, discard badly infested plants, rinse small plants in the sink or shower and wipe larger leaves with a damp cloth, repeating every one to two weeks.[3]
Biological control
Predatory mites, sixspotted thrips, spider mite destroyer lady beetles, minute pirate bugs, bigeyed bugs and lacewing larvae all eat spider mites; protecting them is key.[1][3][2]
Predatory mites can be bought and released. UC IPM suggests about one predator for every 10 spider mites, concentrated in hot spots, after a soap spray if mites are heavy.[1]
Pesticides
If treatment is needed, use insecticidal soap or horticultural oil with thorough coverage of leaf undersides; skip water-stressed plants and days above 90 degrees F. Minnesota advises against homemade soap solutions, which can burn plants.[1][2][3]
Avoid carbaryl, malathion, some pyrethroids such as bifenthrin and permethrin, and soil-applied imidacloprid where mites are a problem: they kill mite predators and can set off spider mite outbreaks.[1][3][2]
Spider mites develop resistance quickly; a review calls the twospotted spider mite the most resistant species by the number of pesticides its populations resist. Most miticides don't kill eggs, so Colorado State says a repeat application about 10 to 14 days later is usually needed.[3][5]
How to check for mites
Hold a sheet of white paper under a branch and shake or tap the foliage; mites fall onto the paper and are easy to see moving.[1][2]
Confirm live mites before treating, because they may be gone by the time damage shows, and plants often recover.[1]
Check garden plants every 3 to 5 days, especially during drought.[2]
Where sources disagree
Size: UC IPM says adult females are less than 1/20 inch long; NC State says the summer female twospotted spider mite is less than 1/50 inch (0.4 mm).[1][4]
Color: NC State describes summer females as greenish yellow; Minnesota describes the twospotted spider mite as yellow-orange.[4][2]
How they spend the winter: UC IPM, Colorado State and NC State say as mated or diapausing adult females in bark cracks and litter; Minnesota says as eggs on vegetation.[1][3][4][2]
Egg laying: Colorado State says mated females may lay a dozen eggs a day for a couple of weeks; NC State says roughly one egg a day.[3][4]
Buying predatory mites: UC IPM says releases can help in large plantings and orchards; Colorado State says they have worked on interior plants but effective outdoor use has not been demonstrated in Colorado, partly because they need humid conditions.[1][3]
Common questions
- Why did spider mites get worse after I sprayed?
- Some broad-spectrum insecticides kill the mites' natural enemies, and some even speed up mite reproduction, leading to outbreaks within days in hot weather.[1][3]
- Are spider mites insects?
- No. They are arachnids, in the same class as spiders and ticks, with eight legs as adults.[1][2]
- Why are spider mites so hard to get rid of on house plants?
- Indoors there are generally no natural enemies and few effective products besides soaps and oils, so you have to treat all plants at once and repeat.[3]
- Does spraying with water really help?
- Yes. A forceful spray on the undersides of leaves knocks off and kills many mites and removes the dust and webbing that protect them.[1][3][2]
Sources
- University of California Statewide IPM Program, “Spider Mites (Pest Notes, Home and Landscape).” ipm.ucanr.edu/home-and-landscape/spider-mites/ (accessed 2026-11-11)
- University of Minnesota Extension, “Twospotted spider mites in home gardens.” extension.umn.edu/yard-and-garden-insects/spider-mites (accessed 2026-11-11)
- Colorado State University Extension, “Spider Mites (Fact Sheet 5.507).” extension.colostate.edu/topic-areas/insects/spider-mites-5-507/ (accessed 2026-11-11)
- NC State Extension, “Twospotted Spider Mite.” content.ces.ncsu.edu/twospotted-spider-mite (accessed 2026-11-11)
- Insect Biochemistry and Molecular Biology, via PubMed, “Acaricide resistance mechanisms in the two-spotted spider mite Tetranychus urticae and other important Acari: a review (Van Leeuwen et al. 2010).” pubmed.ncbi.nlm.nih.gov/20685616/ (accessed 2026-11-11)
- BioEssays, via PubMed, “Spider Mites: Genetic Models to Inform Herbivore and Chelicerate Biology (Clark et al. 2026).” pubmed.ncbi.nlm.nih.gov/42179317/ (accessed 2026-11-11)
- iNaturalist, “Tetranychus urticae taxon page (order and family).” www.inaturalist.org/taxa/203333 (accessed 2026-11-11)