Spider Mites on Indoor Plants: Early Signs and Reliable Treatments

University of Maryland Extension says spider mites suck the chlorophyll from leaves, which leaves fine white spots or stipples. Some species also produce webbing over leaves and stems when populations are high. Webbing is therefore a late sign, so check earlier and look under the leaves.

Mites are about the size of a period on a page. Severe infestations cause yellowing, browning and eventual death of leaves. Check plants with thin, tender leaves regularly by holding each leaf up to the light.

Stippling can also come from other causes, such as thrips or other pests, or plant stress, so confirm before treating. A common home check is to hold a sheet of white paper under a leaf and tap the leaf firmly. Tiny specks that move across the paper suggest mites, and a hand lens makes this easier. Specks that stay still are more likely dust.

Spider mites are generally associated with warm, dry conditions, and heated or air-conditioned rooms can suit them. Mites also reproduce faster as temperatures rise, so a small problem can grow quickly. This is why regular checks matter more than a single treatment.

1. Isolate the plant. Mites can move to nearby plants, so keep the affected one apart.
2. Wash the plant. University of Maryland Extension recommends periodically washing houseplants with a strong spray of water. Rinse both sides of every leaf, in a sink or shower.
3. Use a labeled product if needed. The same source recommends insecticidal soap for houseplants, or a houseplant insecticide labeled for spider mites. Read and follow the label for coverage and how often to repeat.
4. Repeat. Eggs and survivors can restart the population, so keep washing and treating over several weeks, and check the undersides of leaves each time.
5. Clean nearby surfaces. Wipe windowsills and trays near the plant.

Because spider mites favor dry air, raising humidity around vulnerable plants can make conditions less friendly. Grouping plants, using a pebble tray or running a small humidifier can all help locally. This will not clear an infestation by itself, but it can support treatment. A little air movement also helps keep leaf surfaces from staying dusty and still.

Keep checking treated plants every week for at least a few weeks. Look at new growth first. A clean check does not mean the problem is gone for good, so keep inspecting.

If stippling or webbing keeps returning, the mites may be on a nearby plant or in a spot you have not treated. Check and treat every plant in the area at the same time, not one at a time. A plant that has lost most of its leaves despite repeated treatment may be better replaced.

• University of Maryland Extension, "Spider Mites on Indoor Plants"