Common Houseplant Pests in Winter: How to Spot and Treat Them
Spider mites, mealybugs, scale, aphids, whiteflies, and fungus gnats are the usual winter houseplant pests. Here is how to tell them apart, how to confirm...
Published by ThriveThyme
houseplants indoor pests spider mites mealybugs winter
The Short Answer
Most winter houseplant pests arrive on a new plant or ride in on plants that summered outdoors (Colorado State, UMN). Match the symptom to the pest:
| What you see | Likely pest | First move |
|---|---|---|
| Fine pale speckles, bronzing, fine webbing | Spider mites | Rinse leaves, then oil or soap at 5 day intervals |
| White cottony clumps in leaf joints | Mealybugs | Rubbing alcohol on a swab, after a test spot |
| Sticky leaves, brown bumps along veins | Scale | Pick off, then horticultural oil |
| Soft insects bunched on new growth | Aphids | Wash off with water |
| Tiny white flies rise when touched | Whiteflies | Oil on leaf undersides, sticky cards |
| Small dark flies around the soil | Fungus gnats | Let the soil dry, Bti drench |
Use our Houseplant Pest ID tool to go from symptom to treatment in a few clicks.
Spider Mites
UMN Extension calls spider mites the number one houseplant pest. They thrive in warm, dry rooms, which describes most homes in winter. Mississippi State says plants near heating vents and plants that are not watered enough are especially prone.
Signs: Tiny dead spots give the leaf a stippled look. Leaves can turn yellow, bronze, or brown, and heavy infestations cover leaves and stem tips with fine webbing (Mississippi State, Colorado State). Damage often starts on leaf undersides near the veins (Colorado State).
Confirm: Gently tap a leaf over a piece of white paper and look for tiny specks (UMN).
Treat:
- Wash the plant in the shower or sink with a strong spray. Mississippi State suggests repeating every 3 to 5 days. Colorado State says washing over several weeks should bring mites down to low levels.
- Spray horticultural oil, neem oil, or insecticidal soap, covering the leaf undersides, two to three times at 5 day intervals (Mississippi State). Check the oil label before spraying that often. Colorado State rates horticultural oil as probably the most effective spray and soap as only marginal.
- Systemic imidacloprid products do not control spider mites (Mississippi State).
Colorado State says to dispose of heavily infested plants when you can, since they serve as a source for new infestations. UMN notes that succulents, cacti, pothos, snake plant, hoya, and ferns tend to have fewer mite problems, while palms, philodendrons, and figs see more.
Mealybugs
UMN calls mealybugs the second biggest houseplant pest and says they can be nearly impossible to eliminate.
Signs: Soft, oval insects covered in white, waxy, cottony fluff, tucked into leaf joints, stem tips, and leaf undersides, often with sticky honeydew (Wisconsin, UMN). Some species feed on roots. White cottony bits around the drainage holes or a wilting plant can point to root mealybugs (Wisconsin).
Treat:
- Wipe them off with a cotton swab or cloth dipped in rubbing alcohol. Test a small area first. Wisconsin says it may take a day or two for leaf damage to show, and Colorado State warns alcohol can burn leaves.
- A moderately strong spray of warm water knocks off most of them, but rarely all, so check again and repeat (Wisconsin).
- Insecticidal soap or horticultural oil works only where it reaches the insects, and may take several applications (Wisconsin, Mississippi State).
- Keep the plant isolated until the problem is solved (Mississippi State).
Both Wisconsin and Mississippi State say discarding a heavily infested plant is a reasonable choice, and Wisconsin says it is often the most practical fix for root mealybugs.
Scale
Signs: Sticky leaves are usually the first clue. Look on leaf undersides for flat, oval brown bumps, about three sixteenths of an inch long, lined up along the veins (Mississippi State). Brown soft scale is the most common houseplant scale, often on ferns, schefflera, ficus, and orchids.
Treat:
- Where there are only a few, rub or pick them off. Colorado State says even a small disturbance can break a settled scale's mouthparts so it starves.
- Horticultural oil is the most effective spray for scale. Follow the label and plan on several treatments (Colorado State, Mississippi State).
- Soap and alcohol sprays mostly work on young crawlers, not covered adults (Colorado State).
Dead scales can stay stuck in place and look alive, so judge progress by new honeydew and new bumps (Colorado State). Mississippi State says scale is notoriously hard to eliminate, so decide early whether to treat aggressively or discard the plant.
Aphids
Signs: Clusters of small, soft-bodied insects on new growth and leaf undersides, sticky honeydew, distorted leaves, and white shed skins that are often mistaken for live insects (Mississippi State, Colorado State).
Treat: Mississippi State says aphids are easier to control than most houseplant pests. A forceful spray of water, strong enough to wash them off but not damage the plant, works in many cases. Colorado State rates insecticidal soap as effective on aphids.
Whiteflies
Signs: Tiny white winged insects that fly up when you brush the plant, plus flat, see-through, immobile young on the leaf undersides and sticky honeydew (Mississippi State, Colorado State).
Treat: Yellow sticky cards and a small hand vacuum reduce adults, but Mississippi State says you will not succeed by treating only adults. Horticultural oil on the leaf undersides targets the immatures (Mississippi State, Colorado State). Whiteflies almost always come in on a newly bought or gifted plant (Colorado State).
Fungus Gnats
These small dark flies are mostly a nuisance. The larvae live in wet potting mix. Let the soil surface dry between waterings, use yellow sticky traps for adults, and drench with Bacillus thuringiensis israelensis (Bti) for larvae (UMN, Mississippi State, Colorado State). Our full fungus gnats guide covers the details.
Prevent the Next Outbreak
- Quarantine new plants. Colorado State says to keep new plants in a separate area for at least three weeks, then inspect them. Wisconsin suggests keeping new plants apart for a week or so when you can.
- Check plants before they come indoors. See how to check plants for pests before bringing them indoors.
- Scout often. Look under leaves, in leaf joints, and at new growth (UMN, Wisconsin).
- Use the right products. Only use pesticides labeled for houseplants, follow the label, and take plants outside to spray when you can (Colorado State, Mississippi State).
Next Steps
- Identify your pest with the Houseplant Pest ID tool.
- Match light and water to your windows with the Houseplants desk.
- Read how often to water houseplants, since overwatering feeds fungus gnats.
Sources
- University of Minnesota Extension, Houseplant Pests
- Mississippi State University Extension, Insect Pests of Houseplants (P2652)
- Colorado State University Extension, Managing Houseplant Pests
- Wisconsin Horticulture, Mealybugs