The earliest signs of houseplant pests are typically visible on the leaves before you see the pests themselves: stippled or silvery patches from cell damage, sticky residue on leaves or surfaces below the plant, white cottony deposits in stem junctions, or distorted and stunted new growth. Actually seeing the pests requires closer inspection of the undersides of leaves, stem junctions, and growing tips. A regular inspection routine, performed when you water (every week or two), catches infestations at an early stage when they are much easier to treat than when discovered during heavy infestation.
Visual Signs to Look For
Different pests leave different signs on the plant. Learning to recognise what each pest leaves behind is the fastest route to correct identification and effective treatment.
Silvery or bronze stippling on leaves: Spider mites or thrips. Spider mites produce fine webbing between leaves in heavier infestations. Thrips also leave dark frass specks alongside the silver damage.
Sticky residue on leaves or the surface below the plant: Honeydew from sap-sucking insects including mealybugs, scale, aphids, or whitefly. Check for the pest producing the honeydew on the undersides of leaves and stem junctions. See our guide on what causes sticky leaves.
White cottony deposits: Mealybugs. Found in leaf axils, stem junctions, and sometimes in the root zone.
Brown or tan bumps on stems: Scale insects, firmly attached and difficult to remove with a finger. See our guide on treating scale insects.
Small flies from the compost: Fungus gnats. Small dark flies emerging when the pot is moved or watered. See our guide on treating fungus gnats.
Distorted or stunted new growth: Thrips (feeding inside buds before leaves open) or broad mites (too small to see without magnification).
Most pests concentrate on the undersides of leaves and in stem junctions, which are less exposed to light and predators. Flip leaves over and inspect the underside along the midrib. Look into the base of the plant where stems meet. Check the inner side of leaf axils (where the leaf joins the stem) with a torch or phone light.
If you are still struggling to see pests, hold a white piece of paper under the plant and tap or shake the plant briskly. Mites and thrips fall onto the paper and are visible as tiny moving specks against the white background.
When to Inspect More Often
Pest populations grow fastest in warm, dry conditions: summer heat waves, and winter when central heating creates low-humidity environments, are peak periods for spider mites in particular. If your plants are in conditions that favour pest development, inspect more frequently. Plants recently brought in from outdoors (after a summer outside) should be inspected before being placed near other houseplants. See our guide on quarantining new and returning plants.