Spider Mites
Act nowPest · spreads to other plants · also called two-spotted mite, red spider mite
Spider mites are the pest that kills houseplants that were doing fine last month. They thrive in hot, dry, still air — indoor heating in winter is ideal for them — and they reproduce fast enough to go from unnoticed to fatal in a few weeks. By the time webbing is obvious the infestation is advanced.
What it looks like
Fine pale stippling across the leaf, as though it had been sprayed with a very fine dust of pinpricks. Leaves go bronze or grey, and fine webbing appears between leaves and along stems in bad infestations. The mites themselves are just visible as moving specks.
How to confirm it
- Fine even stippling rather than discrete spots or holes.
- Hold a sheet of white paper under a leaf and tap: the specks that fall will move.
- Webbing between leaves and along stems, unlike anything a disease produces.
- Worst in hot dry conditions and on plants near a radiator or vent.
What to do
- 1Rinse the plant thoroughly, undersides included, in a shower or with a hose. Repeat every three days for two weeks to catch newly hatched mites.
- 2Raise humidity around the plant — mites hate it.
- 3Insecticidal soap or horticultural oil, hitting leaf undersides, repeated at intervals.
- 4Isolate an affected houseplant immediately. They spread to everything nearby.
What it gets confused with
One observation settles each of these.
Preventing it next time
- Keep humidity up around houseplants and away from heat sources.
- Rinse foliage occasionally as routine.
- Quarantine new plants for a couple of weeks before adding them to a collection.
Plants affected
Most garden and container plants can be affected.
Check these two things first
- Push a finger into the soil, two knuckles deep. Wet soil plus a wilting plant means too much water, not too little — and it is the commonest reason a plant is dying. Dry soil plus crisp leaves means the opposite. The leaves look nearly identical either way, so the soil is what tells you.
- Turn a damaged leaf over. Half of all diagnoses live on the underside: fuzz means downy mildew, fine webbing means spider mites, clusters of insects mean aphids. Nothing on the top of a leaf is as informative.
Most garden problems are cosmetic and resolve without treatment. Reach for a spray last, not first.