Scale or mealybug infestation
Small brown bumps along the stems, or white cottony tufts and sticky residue, mean sap-sucking pests have moved in.
Diagnosis
Scale or mealybug infestation
What's happening
Scale insects look like tiny, flat, brown limpets stuck to the frond stems and undersides, while mealybugs show up as white, cottony specks in the crevices. Both pierce the fronds and drink the plant's sap, which weakens it, yellows the fronds, and leaves behind a sticky residue called honeydew. The dense, ferny foliage gives them lots of places to hide, so an infestation can build up unnoticed.
How to fix it
Isolate the fern from your other plants right away so the pests don't spread. Wipe off what you can with a cloth, then treat the whole plant — tops and undersides of fronds, stems, and crown — thoroughly. Because fern foliage is delicate, test on a small area first and treat in the evening, out of direct sun, to avoid burning the fronds. Repeat every 7–10 days for several weeks to catch newly hatched crawlers, since pests at every life stage won't all be killed in one pass. Trim out the most heavily infested fronds to lighten the load.
What fixes it
- Insecticidal soap — Insecticidal soap is gentle enough for delicate fern foliage and smothers scale and mealybugs on contact when sprayed thoroughly.
If that doesn't fix it
This is general guidance based on common symptoms; individual plants vary.
Read the full Boston Fern care guide →
Reviewed June 2026 · how we check this