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Tomato russet mite: how to recognise and treat it

Pest

Tomato russet mite — Photo: Goldlocki, CC BY-SA 3.0, Wikimedia Commons

Symptoms

Stems and lower leaves look greasy, then dry out and turn bronze; the damage starts at the base and moves up the plant.
Leaves curl, turn yellow or bronze, sometimes glossy underneath, then wither and drop.
Fruit skin turns bronze and may crack lengthwise.
No webbing; the mites are too small to see without a strong hand lens. Untreated plants can die in hot, dry weather.

Organic treatment

Sulfur dust or wettable sulfur, covering the lower stems and leaves well; not above 32 °C, not on flowering plants and not near an oil spray.
Neem oil (azadirachtin); it works only where it touches the mites, so cover the foliage thoroughly.
In a greenhouse, release the predatory mite Amblyseius andersoni while numbers are still low.

Chemical treatment

An acaricide with abamectin; in many countries it is for professional use only, so check what is approved for home gardens and follow the label dose and pre-harvest interval.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Prevention

From midsummer check the lower stems with a hand lens, and the green leaves just above any bronzing.
Remove nightshades, bindweed and other weed hosts, and do not grow tomatoes next to petunias or potatoes.
Clear crop debris after harvest and keep no solanaceous plants in the greenhouse over winter — the mites need living hosts.
Work on infested plants last and wash hands and tools afterwards, as mites spread on clothing and equipment.

Plants it affects

Sources

Figures checked against these sources.