Lemon 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 Lemon (Citrus x limon), using what its sources say about pests and diseases, humidity and watering and 3 problems recorded for it.
Sources last read 14 September 2026.
The lemon is a species of small evergreen tree in the Citrus genus of the flowering plant family Rutaceae. A true lemon is a hybrid of the citron and the bitter orange. Wikipedia, CC BY-SA 4.0
Native range: as a cultigen derived from artificial hybrids. (subtropical). Also sold as bergamot, bergamot orange, Chinese dwarf lemon, dwarf lemon, lemandarin and mandarin lime.
What Lemon’s sources say that bears on this
- Pests and diseases
- Greenhouse red spider mite, mealybugs and scale insects can attack it. Disease is uncommon.RHS · read 13 September 2026
- Humidity
- ASHRAE recommends indoor relative humidity between 30% and 60%Penn State Extension · read 13 September 2026
- Watering
- In the growing season they need lots of water plus small, regular doses of nitrogen fertilizer to boost growth and fruit size.NC State Extension · read 13 September 2026While growing in spring and summer, water generously and mist every day. Use a citrus fertiliser all year round as directed by the manufacturer; give little water in winter.RHS · read 13 September 2026
How this shows up on a Lemon
Fine pale speckling on the leaves, then webbing at the tips: spider mites
Speckling spreads over the lemon until the leaves look washed out and bronze, with fine threads at the growing points.
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 2026Hard, rounded scale on the undersides of the leaves
The lemon is sticky to the touch and yellows slowly. Along the veins on the undersides sit small shell-like scales that lift off with a fingernail.
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: Whether the bumps sit on the veins. Scale follows the sap; spots from disease scatter across the leaf.
RHS · read 13 September 2026Sticky leaves and white fluff where they meet the stem: mealybugs
The lemon carries white, cottony specks in its crevices, and growth slows. Leaves beneath the colonies turn sticky and, in time, dull or yellow.
RHS lists mealybugs among the pests it may attract. The wax keeps them dry and hard to reach, so they multiply in the sheltered joints of the canopy.
Telling it apart: Where the white is. Mealybugs gather in joints and under leaves; a powdery coating across the top of a leaf is mildew.
RHS · read 13 September 2026Possible causes, likeliest first for a Lemon
Most likely spider mites
Ranked higher because Lemon's recorded problems point this way.
- Fine pale speckling on the leaves, then webbing at the tips: spider mites RHS
Why: Spider mites feed on individual leaf cells, and each emptied cell shows as a pale speck.
What to try:
- Move the lemon 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 Lemon's recorded problems point this way.
- Sticky leaves and white fluff where they meet the stem: mealybugs RHS
Why: Mealybugs are soft insects that cover themselves in white wax, which gives the cottony look.
What to try:
- Move the lemon 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 scale insects
Ranked higher because Lemon's recorded problems point this way.
- Hard, rounded scale on the undersides of the leaves RHS
Why: Scale insects settle in one place under a hard or waxy shell and feed on sap.
What to try:
- Move the lemon 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 lemon does not move.
Less likely for a Lemon, still possible
Questions
- What usually causes pests on a Lemon?
- For Lemon: spider mites, mealybugs and scale insects.
- How can I tell which one it is on my Lemon?
- 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 Lemon's sources say about its pests and diseases?
- RHS: Greenhouse red spider mite, mealybugs and scale insects can attack it. Disease is uncommon.
- What does this look like on a Lemon?
- Speckling spreads over the lemon until the leaves look washed out and bronze, with fine threads at the growing points. Telling it apart: Where the damage starts. Mites stipple the whole leaf in fine dots; sun scorch bleaches the side facing the window.
- Is Lemon 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
CalamondinCurled, sticky new leaves with green or black insects: aphids
AvocadoPale stippled leaves and tiny moving dots underneath: a mite pest
Bay laurelRagged, eaten leaves and rolled leaves: an insect pest
Chinese banyanPale stippled leaves and tiny moving dots underneath: a mite pest
Coffee plantFine pale speckling on the leaves, then webbing at the tips: spider mites
Common figDull, finely mottled leaves and faint webs: spider mites
Something else wrong with the Lemon?
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.