Nasturtium 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 Nasturtium (Tropaeolum majus), using what its sources say about pests and diseases and humidity and 4 problems recorded for it.
Sources last read 14 September 2026.
Tropaeolum majus, the garden nasturtium, nasturtium, Indian cress or monk's cress, is a species of flowering plant in the family Tropaeolaceae. An annual or a short-lived perennial with disc-shaped leaves and brilliant yellow, orange or red flowers, it is of cultivated, probably hybrid origin. Wikipedia, CC BY-SA 4.0
Native range: as a cultigen from Peru (subtropical). Also sold as Brunnenkress, Common Nasturtium, Garden Nasturtium, greater Indian-cress, Indian cress and Mexican Cress.
What Nasturtium’s sources say that bears on this
- Pests and diseases
- Can be troubled by aphids, whiteflies and mealybugs. Diseases: southern bacterial wilt.NC State Extension · read 13 September 2026Can be troubled by greenhouse red spider mite, greenhouse whitefly and whitefly. Diseases: virus diseases can occur.RHS · read 13 September 2026
- Humidity
- ASHRAE recommends indoor relative humidity between 30% and 60%Penn State Extension · read 13 September 2026
How this shows up on a Nasturtium
Pale stippled leaves and tiny moving dots underneath: a mite pest
The leaves of the nasturtium lose their shine and fill with tiny pale dots. In a heavy infestation fine webbing strings across the shoot tips.
RHS lists spider mites among the pests it may attract. Heated rooms suit them: dry, warm air speeds each generation, and the damage builds within weeks.
Telling it apart: Where the damage starts. Mites stipple the whole leaf in fine dots; sun scorch bleaches the side facing the window.
RHS · read 13 September 2026Sticky buds and shoot tips crowded with small insects
Aphids gather on the undersides of new leaves and around buds on the nasturtium, leaving honeydew and shed skins behind.
NC State Extension lists aphids among the pests it may attract. They feed on the sap of soft new growth, which distorts it, and they multiply quickly without mating.
Telling it apart: What the white bits are. Aphids leave papery cast skins; mealybugs leave wax with an insect inside.
NC State Extension · read 13 September 2026Sticky, yellowing leaves and a cloud of white insects: whitefly
The leaves of the nasturtium yellow and grow sticky, sometimes dusted black, and white insects rest on the undersides.
RHS lists whitefly among the pests it may attract. Their honeydew is what makes the leaves sticky and lets a black film grow on them.
Telling it apart: Stickiness with flying insects. Whitefly has both; fungus gnats fly but leave no honeydew.
RHS · read 13 September 2026White, cottony tufts in the joints of the leaves: mealybugs
Clusters of white wax sit where each leaf joins the stem and along the undersides of the nasturtium. Lifted with a cotton swab, each tuft holds a soft, pale insect, and the leaves below are sticky.
NC State Extension lists mealybugs among the pests it may attract. Mealybugs pierce the stem and draw sap, which weakens new growth and leaves a sticky residue.
Telling it apart: Wipe a tuft with a cotton swab. An insect smears or crawls; a mineral deposit or a hair does not.
NC State Extension · read 13 September 2026Possible causes, likeliest first for a Nasturtium
Most likely spider mites
Ranked higher because Nasturtium's recorded problems point this way.
- Pale stippled leaves and tiny moving dots underneath: a mite pest RHS
Why: Spider mites feed on individual leaf cells, and each emptied cell shows as a pale speck.
What to try:
- Move the nasturtium 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
Ranked higher because Nasturtium's recorded problems point this way.
- White, cottony tufts in the joints of the leaves: mealybugs NC State Extension
Why: Mealybugs are soft insects that cover themselves in white wax, which gives the cottony look.
What to try:
- Move the nasturtium 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.
Most likely aphids
Ranked higher because Nasturtium's recorded problems point this way.
- Sticky buds and shoot tips crowded with small insects NC State Extension
Why: Aphids cluster on soft new growth and flower buds, where the sap is easiest to reach.
What to try:
- Rub them off with fingers, or rinse them off in a sink or shower.
- Repeat every few days while new ones appear.
What would settle it: Look for the pale shed skins among the insects. Aphids molt as they grow, and the skins are left behind in the colony.
Less likely for a Nasturtium, still possible
Questions
- What usually causes pests on a Nasturtium?
- For Nasturtium: spider mites, mealybugs and aphids.
- How can I tell which one it is on my Nasturtium?
- 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 Nasturtium's sources say about its pests and diseases?
- NC State Extension: Can be troubled by aphids, whiteflies and mealybugs. Diseases: southern bacterial wilt. RHS: Can be troubled by greenhouse red spider mite, greenhouse whitefly and whitefly. Diseases: virus diseases can occur.
- What does this look like on a Nasturtium?
- The leaves of the nasturtium lose their shine and fill with tiny pale dots. In a heavy infestation fine webbing strings across the shoot tips. Telling it apart: Where the damage starts. Mites stipple the whole leaf in fine dots; sun scorch bleaches the side facing the window.
- Is Nasturtium safe to handle while I check it?
- Its sources list it as toxic to people. Wash your hands after handling the roots or sap, and keep trimmings away from pets.
Other plants that show pests
African violetIrregular notches bitten from leaf edges by an insect pest
Barberton daisyCurled, sticky new leaves with green or black insects: aphids
Bearded irisRagged holes and slime trails: a slug or snail pest
Bigleaf hydrangeaClusters of small soft insects on the shoot tips and buds: aphids
Bird of paradiseDull, finely mottled leaves and faint webs: spider mites
Blue passion flowerPale stippled leaves and tiny moving dots underneath: a mite pest
Something else wrong with the Nasturtium?
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.