Tomato russet mite
An eriophyid mite only about 0.2 mm long; you need at least a 14× hand lens to see it. It feeds on the surface of tomato stems, leaves and fruit, which look greasy and then turn bronze, starting at the base of the plant and moving up. The lower leaves dry out, and a heavy infestation can strip or kill the plant. By the time the bronzing is noticed, there may be hundreds of mites on the green leaves just above it. Sulfur, as dust or a wettable powder, is the standard control. No commercially sold predator has yet proven effective on tomato, because the plant's sticky hairs keep predatory mites out.
Bronzed tomato stem and leaves from Aculops lycopersici feeding, with an inset of the mites under magnification. Photo: pending.
Identification
The mites are about 0.2 mm long (sources give 0.14–0.3 mm), cone- or wedge-shaped, and yellowish, tan or pink. UC IPM says a 14× hand lens is the minimum to see them. Look on the green leaves and stems just above the bronzed area: the mites keep moving up the plant ahead of the most obvious damage.
Spider mites are larger and rounder, usually carry two dark spots and often spin webbing. Predatory mites are clear and move quickly (UC IPM). Finding the mites under a lens is the confirmation.
Easily confused with
- Two-spotted spider miteAlso a pestSpider mites are rounder and larger, usually with two dark spots, and often spin webbing. Russet mites are conical, yellowish-tan or pink, and need a 14× lens.
- Predatory mitesBeneficial — leave itPredatory mites are clear-bodied and move rapidly; russet mites are conical and yellowish, tan or pink.
Damage symptoms
Russet mites empty the cells of the leaf and stem surface. Because the damage starts low on the plant and the mites are invisible, it usually goes unnoticed until the lower plant is bronzed. Left alone, it can kill the plant. A 2022 Spanish paper, summarising earlier work, notes that in greenhouses the mite can dry up to 79% of the leaves, and that yield losses of 25% to 100% have been reported depending on the infestation. Fruit is usually not attacked in gardens, but heavily infested plants can have russeted young fruit.
- A greasy look on the lower stems and leaves, turning bronze or russet
- Damage that starts at the base of the plant and moves upward
- Lower leaves drying out and dying
- Stems losing their hairs and turning brown, sometimes with small cracks
- Defoliation in hot weather, with fruit left exposed to sunburn
Lifecycle & degree days
Russet mites breed very fast in heat. Biobest researchers report populations doubling in under three days at 77 °F (25 °C), which is why a problem seems to appear overnight. In California fields, damage is typically first seen once green fruit reach about 1 in across, and rarely after a quarter of the fruit has ripened. In gardens it shows in mid to late summer on half-grown or larger plants. The mites spread passively, on air currents, on people working in the crop, and in the plant trade. Nightshade-family weeds and crops, and morning glory, act as alternate hosts.
- Size
- About 0.2 mm (0.14–0.3 mm); 14× lens minimum
- Population doubling
- Under 3 days at 77 °F (25 °C)
- First damage (field)
- When green fruit reach about 1 in
- Garden timing
- Mid to late summer
- Spread
- Air currents, people working the crop, plant trade
Host crops
A tomato specialist that also lives on other members of the nightshade family. UC IPM names petunia and potato as hosts, and nightshades and morning glory as alternate weed hosts to remove where it recurs. It is found almost everywhere solanaceous crops are grown, and it has become a major tomato pest worldwide over the last decade, in open fields and in greenhouses.
Monitoring & action thresholds
UC IPM gives no numeric threshold. UC IPM's rule for commercial tomato is to mark the edges of each bronzed patch and check again in 2–3 days. Treatment is needed at once if the damage is spreading. In a garden, the same logic applies: bronzing that is moving up the plant, or appearing on new plants, calls for sulfur.
From the time the first green fruit are about 1 in across, look at the lower stems and leaves for a greasy or bronzed look. Then check the damaged leaves, and the green leaves just above them, with a 14× lens or stronger. In a field, mark the boundaries of each infested patch and recheck in 2–3 days to see whether it is growing. Look again after hot spells, when populations explode.
Biological control
No purchased predator is ready to recommend for tomato russet mite, which is why this page lists no biological control. Tomato's glandular hairs deter the common predatory mites, while the russet mite, at 0.2 mm, shelters among them. In earlier trials cited by Biobest researchers (Pijnakker et al. 2022), curative releases of 140 and 420 Swirski mites per plant did not reduce the pest. Neoseiulus californicus, Amblyseius andersoni and N. fallacis showed promise at reducing the pest in curative releases, but they could not establish, so the repeated releases needed were judged too expensive for growers. Bioline's Anderline page does list tomato russet mite as a target of A. andersoni, so suppliers and researchers disagree; the trial record is why we do not recommend it. A 2024 study states that no commercial beneficial had yet proven effective. The most promising candidates are tiny iolinid mites such as Pronematus ubiquitus, which move between the hairs. Established ahead of the pest and fed pollen, they cut russet mite numbers by 98% in a greenhouse trial by Swiss researchers, although their own numbers fell over the season, probably from lack of food and high temperatures. Transeius montdorensis, supplied with extra prey mites, also reduced the pest and raised yield in Spanish trials. We have not confirmed that either is sold in the US.
Cultural controls
Hosts and hygiene are the cultural levers, because the mite moves between nightshade-family plants and travels on people and tools.
- Do not grow tomatoes next to petunias, potatoes or other nightshade-family plants, which also host the mite
- Where it recurs in the same field, clear weed hosts such as nightshades and morning glory
- Check the base of the plants from the time green fruit are about 1 in across, and act as soon as bronzing spreads
- Enter infested plantings last, since the mites can be carried by people working in the crop
- Stem barriers of oil, insect glue or diatomaceous earth slowed the mites' climb in German potted-plant trials, but in a greenhouse crop the effect lasted only about two weeks
Chemical, last resort
- Sulfur (dust or wettable)REI 24 h
- AbamectinREI 12 h
Rating: the effect on this pest's natural enemies if a spray hits them or they feed on treated plants. REI is the re-entry interval on farm and greenhouse labels; home labels usually give none, so follow the label.
Sources
UC IPM Pest Management Guidelines: Tomato — Tomato Russet Mite (text 2013, table 2016)
UC IPM, Tomato Russet Mite (Home and Landscape)
Vervaet et al., Is the emerging mite pest Aculops lycopersici controllable?, Pest Manag. Sci. 2021
Pijnakker et al., Phytoseiid and iolinid mites for biological control of TRM, Insects 2022
Maret et al., Pronematus ubiquitus curbs Aculops lycopersici damage, Pest Manag. Sci. 2024
Castañé et al., Control of Aculops lycopersici with Transeius montdorensis, Insects 2022
Böckmann et al., Restriction of russet mite using stem barriers in tomato, Exp. Appl. Acarol. 2025
UC IPM, Relative Toxicities of Insecticides and Miticides Used in Tomatoes to Natural Enemies (2016)
Bioline AgroSciences: Anderline (Amblyseius andersoni) product page (accessed Sept 2026)
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
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