Pests problem

How to Identify and Get Rid of Spider Mites

Spider mites are nearly microscopic pests that cause fine yellow stippling on leaves and spin delicate webbing between stems. They thrive in hot, dry indoor air.

Spider mites are tiny arachnids, not insects, most commonly the two-spotted spider mite (Tetranychus urticae). At under 1/50 inch they are barely visible to the naked eye, appearing as moving specks of red, brown, or green on the undersides of leaves. They pierce plant cells and suck out the contents, leaving behind the speckled, faded look that is usually the first clue an infestation is underway.

These pests explode in warm, dry conditions, exactly the environment created by indoor heating in winter. A single female can lay dozens of eggs, and a generation can complete in as little as a week at 80 F, so a small population can become a leaf-covering colony in two to three weeks. Catching them early, before fine silk webbing appears, makes them far easier to eliminate.

Signs to look for

  • Fine yellow or white stippling and a faded, dusty appearance on upper leaf surfaces
  • Delicate silk webbing in leaf axils, along stems, or across leaf undersides
  • Tiny moving dots on the underside of leaves, visible against white paper when tapped
  • Leaves turning bronze, dry, and brittle, then dropping in heavy infestations
  • Overall loss of vigor and stalled growth as feeding damage spreads

What causes it

Hot, dry indoor air

Low humidity and temperatures of 70 to 85 F let spider mites reproduce rapidly. Plants near heating vents, radiators, or sunny windows in winter are especially prone.

Dusty, stressed, or under-watered plants

Drought-stressed and dusty foliage is more susceptible. Dust also shelters mites and makes infestations harder to spot until damage is widespread.

Introduction from new plants

Mites and eggs frequently hitchhike in on newly purchased plants or fresh cut flowers and spread to neighbors that are touching or nearby.

Lack of inspection on leaf undersides

Because mites live and feed on the underside of leaves, infestations often go unnoticed until webbing or heavy stippling appears, by which point the colony is large.

How to fix it

  1. 1
    Isolate the plant immediately

    Move the infested plant away from all others. Spider mites spread easily by crawling and on air currents, so quarantine is the first step to protect your collection.

  2. 2
    Rinse the plant thoroughly with water

    Take the plant to a sink or shower and spray all leaf surfaces, especially the undersides, with a strong stream of room-temperature water to physically knock off mites, eggs, and webbing.

  3. 3
    Spray with insecticidal soap or horticultural oil

    Coat every surface, top and bottom, with insecticidal soap or neem oil until dripping. These work on contact, so complete coverage of the undersides is essential.

  4. 4
    Repeat treatment every 5 to 7 days for three weeks

    Because eggs survive a single spray, reapply on a 5-to-7-day cycle for at least three rounds to catch newly hatched mites before they mature and breed.

  5. 5
    Raise humidity around the plant

    Group plants together, run a humidifier, or set the pot on a pebble tray to push humidity above 50%. Spider mites struggle to reproduce in humid air.

  6. 6
    Prune out heavily webbed foliage

    Cut away and bag the most damaged, web-covered leaves to remove large numbers of mites and eggs at once, then continue spray treatments on the remaining growth.

How to prevent it

  • Keep humidity above 50% and mist or shower foliage periodically in dry winter months
  • Wipe dust off leaves regularly so you can spot mites early and remove their cover
  • Inspect leaf undersides weekly, tapping a leaf over white paper to check for moving specks
  • Quarantine new plants for two weeks before adding them to your collection
  • Keep plants well watered and out of hot, dry drafts to reduce stress

Plants prone to this

Calathea OrbifoliaAreca PalmEnglish Ivy

Related problems

Why Are My Plant’s Leaves Pale or Washed Out?Pale, washed-out, or light green leaves usually mean too little light, though nutrient deficiency and overwatering can also cause it. Here is how to find the cause and restore rich color.Why Are My Plant's Leaves Going Crispy?Crispy, brittle leaves mean the plant is losing moisture faster than it can replace it, usually from dry air, underwatering, or too much sun. The fix is steadier water and a gentler environment.Why Are My Plant's Leaves Turning Yellow?Yellowing leaves (chlorosis) are most often caused by overwatering, but light, nutrients and natural aging can all play a role. Here's how to find the real cause and fix it.

FAQ

How do I know if it's spider mites and not just dust?

Tap a suspect leaf over a sheet of white paper. If you see tiny moving specks, those are mites. Fine webbing in leaf axils and a stippled, faded look on the upper leaf surface also confirm spider mites rather than dust.

Will spider mites spread to my other plants?

Yes, very easily. They crawl between touching plants and ride on air currents, so isolate any infested plant right away and check neighbors for early stippling.

Why do spider mites keep coming back after I treat them?

A single spray does not kill the eggs. You need to repeat treatment every 5 to 7 days for at least three weeks to catch each new generation, and you should also raise humidity to make the environment hostile to them.