Spider mites are tiny — easy to miss until you see the damage. Getting on top of them early is straightforward, and the conditions they thrive in are the real lever: extension horticulture confirms dry indoor air and reduced plant vigour favour the mites (Iowa State Extension).
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How to identify spider mites
Look for these together:
- Stippling — leaves “speckled with very tiny yellowish-green spots” (Iowa State Extension).
- Discolouration — over time leaves turn greenish-yellow, then tan or brown (Iowa State Extension).
- Fine webbing on leaves and stems is a strong confirmation (Iowa State Extension).
You’ll usually see damage and webbing before the mites themselves. Inspect both leaf surfaces.
Why they’re here — the conditions
Spider mites flourish in dry indoor air on stressed plants (Iowa State Extension). Heated rooms and dry vents are classic triggers — treating conditions matters as much as treating mites.
Prevention-first management
- Isolate the affected plant.
- Rinse the foliage with water — extension: “washing or syringing infested plant foliage may reduce light mite populations” (Iowa State Extension). Lukewarm, both surfaces, in the shower/sink.
- Raise local humidity (group plants, humidifier, pebble tray) — mites prefer dry air.
- Insecticidal soap when rinsing isn’t enough; commercial insecticidal soap is preferred (avoid dishwashing detergent) (Iowa State Extension). Treatments commonly need to be repeated because of the mites’ life cycle.
When a plant is too far gone
If heavily webbed and severely stippled, the kindest realistic move is to discard the plant and protect the rest of the collection — propagate a clean cutting where feasible. Honest beats nursing a hopeless case while it seeds your shelf.
Stop it coming back
Quarantine new plants for a couple of weeks. Keep plants healthy: right light, correct watering. Manage room humidity in winter.
Related: Why Are My Plant Leaves Curling? (mites are one cause), the Troubleshooting hub, and Plant Care Basics.