Boston fern pests, webbing or sticky leaves: causes and what to do
6 results in the diagnosis tree begin with pests, 5 of them marked likely when the answers fit. They are ordered here for Boston fern (Nephrolepis exaltata), using what its sources say about pests and diseases, humidity and watering and 2 problems recorded for it.
Sources last read 14 September 2026.
Nephrolepis exaltata, known as the sword fern or Boston fern, is a species of fern in the family Nephrolepidaceae. It is native to the Americas. Wikipedia, CC BY-SA 4.0
Native range: Trop. & Subtrop. America (subtropical). Also sold as boss fern, Boston swordfern, Bostonfern, Fluffy Ruffles, ladder fern and Wild Boston Fern.
What Boston fern’s sources say that bears on this
- Pests and diseases
- Can be troubled by Florida fern caterpillar and fern scale.NC State Extension · read 13 September 2026Scale insects can attack it. Disease is uncommon, but fronds that stay too wet can rot.RHS · read 13 September 2026
- Humidity
- ASHRAE recommends indoor relative humidity between 30% and 60%Penn State Extension · read 11 September 2026
- Watering
- Water less in winter, since the plant is dormant then and excess water can cause root rot.NC State Extension · read 13 September 2026In the growing season, water moderately using soft water and feed monthly with a balanced liquid fertiliser at half strength. Give little water in winter.RHS · read 13 September 2026
How this shows up on a Boston fern
Ragged, eaten fronds and rolled leaves: an insect pest
The boston fern loses leaf tissue quickly. Caterpillars hide on the undersides or inside rolled fronds.
NC State Extension lists caterpillars among the pests it may attract. Moth and butterfly larvae eat leaf tissue, and some fold leaves around themselves for shelter.
Telling it apart: Holes or notches. Caterpillars eat through the leaf; vine weevil adults bite notches from the edge.
NC State Extension · read 13 September 2026Sticky leaves and immobile shell-like insects on the stems
Rows of small, hard scales sit where the veins of the boston fern are thickest, and the surface below them is glossy with honeydew.
RHS lists scale insects among the pests it may attract. The insect settles under a waxy shell and feeds on sap for life, so a colony builds quietly along the stems.
Telling it apart: Stickiness below the bumps. Scale drips honeydew; a leaf spot is dry.
RHS · read 13 September 2026Possible causes, likeliest first for a Boston fern
Most likely scale insects
Ranked higher because Boston fern's recorded problems point this way.
- Sticky leaves and immobile shell-like insects on the stems RHS
Why: Scale insects settle in one place under a hard or waxy shell and feed on sap.
What to try:
- Move the boston fern away from other plants.
- Scrape the scales off with a fingernail or a soft brush, then wipe the stems and leaves.
What would settle it: Push a bump gently with a fingernail. Scale comes away and leaves a mark; a bump that is part of the boston fern does not move.
Most likely spider mites
Why: Spider mites feed on individual leaf cells, and each emptied cell shows as a pale speck.
What to try:
- Move the boston fern away from other plants.
- Wash the leaves, top and underside, with a strong spray of water in a shower or sink.
What would settle it: Hold a sheet of white paper under a leaf and tap the leaf. Tiny specks that move across the paper are mites.
Most likely mealybugs
Why: Mealybugs are soft insects that cover themselves in white wax, which gives the cottony look.
What to try:
- Move the boston fern away from other plants.
- Wipe off every insect you can see with a cotton swab dipped in rubbing alcohol, testing a single leaf first.
What would settle it: Touch a tuft with a cotton swab. If a small, pale, oval insect is underneath, it is a mealybug.
Less likely for a Boston fern, still possible
Questions
- What usually causes pests on a Boston fern?
- For Boston fern: scale insects, spider mites and mealybugs.
- How can I tell which one it is on my Boston fern?
- What can you see? Fine webbing, and tiny pale speckles on the leaves; White, cottony tufts in the leaf joints; Small brown or pale bumps on stems and leaves that do not move; Clusters of small, soft insects on the new growth; Tiny dark flies around the soil; Sticky, shiny residue, but no insect I can see.
- What do Boston fern's sources say about its pests and diseases?
- NC State Extension: Can be troubled by Florida fern caterpillar and fern scale. RHS: Scale insects can attack it. Disease is uncommon, but fronds that stay too wet can rot.
- What does this look like on a Boston fern?
- The boston fern loses leaf tissue quickly. Caterpillars hide on the undersides or inside rolled fronds. Telling it apart: Holes or notches. Caterpillars eat through the leaf; vine weevil adults bite notches from the edge.
Other plants that show pests
AlocasiaFine pale speckling on the leaves, then webbing at the tips: spider mites
Aloe veraSticky leaves and immobile shell-like insects on the stems
Areca palmDull, finely mottled fronds and faint webs: spider mites
Arrowhead plantCurled, sticky new leaf blades with green or black insects: aphids
Asparagus fernCurled, sticky new fronds with green or black insects: aphids
Bird's nest fernSticky leaves and immobile shell-like insects on the stems
Something else wrong with the Boston fern?
What this does not cover
This page orders a decision tree's results using a plant's sourced care. It has not seen your plant, its pot or its window, and two problems at once are common: that is the usual reason a confident answer turns out wrong. The questions in the diagnosis tool narrow it further than a list can.