Japanese maple 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 Japanese maple (Acer palmatum), using what its sources say about pests and diseases, humidity and watering and 4 problems recorded for it.
Sources last read 14 September 2026.
Acer palmatum, commonly known as Japanese maple, palmate maple, or smooth Japanese maple, is a species of woody plant native to Korea, Japan, China, eastern Mongolia, and far eastern Russia. Many different cultivars of this maple have been selected and they are grown worldwide for their large variety of attractive forms, leaf shapes, and spectacular colors. Wikipedia, CC BY-SA 4.0
Native range: SW. Korea, C. & S. Japan (temperate). Also sold as Japanese Maple Cultivars and smooth Japanese maple.
What Japanese maple’s sources say that bears on this
- Pests and diseases
- Can be troubled by Japanese maple scale (Lopholeucaspis japonica; Hemiptera: Diaspididae), aphids, Japanese maple leafhopper and other maple insect pests. Diseases: common maple diseases.NC State Extension · read 13 September 2026Can be troubled by caterpillars, horse chestnut scale, aphids and Acer gall mite. Diseases: honey fungus, acer leaf scorch and Verticillium wilt can occur.RHS · read 13 September 2026
- Humidity
- ASHRAE recommends indoor relative humidity between 30% and 60%Penn State Extension · read 13 September 2026
- Watering
- In summer, water when needed.RHS · read 13 September 2026
How this shows up on a Japanese maple
Leaves eaten away and webbed together: caterpillars
Chewed leaves on the Japanese maple come with green or brown caterpillars nearby, often active at night.
RHS lists caterpillars among the pests it may attract. Their damage is chewing, not sucking, so the tissue is gone rather than discolored.
Telling it apart: Whether tissue is missing. Chewing pests remove it; sap-feeders only discolor it.
RHS · read 13 September 2026Pale flecks on the leaves and insects that leap away: leafhoppers
Touching the Japanese maple sends small, wedge-shaped insects leaping. The leaves they fed on are mottled pale.
NC State Extension lists leafhoppers among the pests it may attract. They feed on the undersides and leap off when disturbed, so they are rarely seen at rest.
Telling it apart: The size of the flecks. Leafhopper flecks are coarser than the fine stipple mites leave.
NC State Extension · 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 Japanese maple, leaving honeydew and shed skins behind.
RHS 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: Whether you can see them. Aphids are visible to the eye; the mites that distort new growth are not.
RHS · read 13 September 2026Sticky leaves and immobile shell-like insects on the stems
Rows of small, hard scales sit where the veins of the Japanese maple 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 Japanese maple
Most likely scale insects
Ranked higher because Japanese maple'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 japanese maple 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 japanese maple does not move.
Most likely aphids
Ranked higher because Japanese maple's recorded problems point this way.
- Sticky buds and shoot tips crowded with small insects RHS
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.
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 japanese maple 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.
Less likely for a Japanese maple, still possible
Questions
- What usually causes pests on a Japanese maple?
- For Japanese maple: scale insects, aphids and spider mites.
- How can I tell which one it is on my Japanese maple?
- 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 Japanese maple's sources say about its pests and diseases?
- NC State Extension: Can be troubled by Japanese maple scale (Lopholeucaspis japonica; Hemiptera: Diaspididae), aphids, Japanese maple leafhopper and other maple insect pests. Diseases: common maple diseases. RHS: Can be troubled by caterpillars, horse chestnut scale, aphids and Acer gall mite. Diseases: honey fungus, acer leaf scorch and Verticillium wilt can occur.
- What does this look like on a Japanese maple?
- Chewed leaves on the Japanese maple come with green or brown caterpillars nearby, often active at night. Telling it apart: Whether tissue is missing. Chewing pests remove it; sap-feeders only discolor it.
Other plants that show pests
AvocadoPale stippled leaves and tiny moving dots underneath: a mite pest
Bay laurelRagged, eaten leaves and rolled leaves: an insect pest
CalamondinCurled, sticky new leaves with green or black insects: aphids
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 Japanese maple?
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.