Spider Mites
Spider mites are nearly invisible sap-suckers that thrive in warm, dry indoor air -- exactly the conditions of a heated home in winter. They pierce leaf cells one by one, leaving a telltale pale stippling, and by the time fine webbing appears the colony is well established. Fast, repeated treatment saves the plant; ignoring them rarely ends well.
Quick Diagnosis
Look for fine pale speckling (stippling) on leaf surfaces, dusty-looking undersides, and in advanced cases delicate webbing at leaf joints and along edges. Confirm by holding white paper under a leaf and tapping: dislodged mites appear as moving specks. Leaves eventually bronze, dry, and drop.
Causes
Understanding the root cause is the first step to fixing the problem.
- 1Hot, dry air -- mite populations explode below 40% humidity.
- 2New plants, cut flowers, or summering-outdoors plants carrying mites inside.
- 3Drought-stressed plants, which are more attractive and less resistant to mites.
- 4Proximity to infested plants -- mites walk between touching leaves and ride air currents.
- 5Winter heating shrinking humidity while radiators warm the foliage.
Treatment Steps
Follow these steps to treat spider mites in your indoor plants.
- 1
Isolate the plant immediately -- mites spread readily.
- 2
Shower the entire plant with lukewarm water, scrubbing leaf undersides gently, to physically remove most of the colony.
- 3
Spray thoroughly with insecticidal soap, neem oil, or horticultural oil, coating every leaf underside.
- 4
Repeat treatment every 5-7 days for at least 3 weeks -- eggs hatch continuously and are untouched by sprays.
- 5
Raise humidity and lower temperature to slow reproduction while you treat.
- 6
Discard severely infested, declining plants rather than risk your whole collection.
Prevention Tips
Keep your plants healthy by following these preventive measures.
- Keep humidity above 40-50%, especially in winter.
- Inspect leaf undersides whenever you water.
- Quarantine new plants for two weeks.
- Shower dust-prone plants (ivy, calathea, dracaena) every month or two.
- Keep plants well watered -- drought stress invites mites.