Japanese Maple Problems – Pests And Diseases For Japanese Maple Trees

Japanese Maple Problems – Pests And Diseases For Japanese Maple Trees

By: Jackie Rhoades

A Japanese maple is a glorious specimen tree. Its red, lacy leaves are a welcome addition to any garden, but they aren’t problem free. There are a few Japanese maple diseases and several insect problems with Japanese maples that you should be aware of to give your tree the care it needs.

Japanese Maple Pests

There are several possible insect problems with Japanese maples. The most common Japanese Maple pests are the Japanese beetles. These leaf feeders can destroy the looks of a tree in a matter of weeks.

Other Japanese maple pests are scale, mealybug and mites. While these Japanese maple pests can attack a tree of any age, they are usually found in young trees. All of these pests present as tiny bumps or cottony dots on twigs and on leaves. They often produce a honeydew which attracts another Japanese maple problem, sooty mold.

Wilting leaves, or leaves that are curled and puckered, may be a sign of another common Japanese maple pest: aphids. Aphids suck plant sap from the tree and a large infestation can cause distortions in tree growth.

Tiny clumps of sawdust indicate borers. These pests drill into the bark and tunnel along the trunk and branches. At worst, they can cause the death of branches or even the tree itself by girdling the limb with their tunnels. Milder cases can cause scarring.

A strong spray of water and regular treatment with either chemical or organic pesticides will go a long way to prevent insect problems with Japanese maples.

Japanese Maple Tree Diseases

The most common Japanese maple diseases are caused by fungal infection. Canker can attack through bark damage. Sap oozes from the canker in the bark. A mild case of canker will resolve itself, but heavy infection will kill the tree.

Verticillium wilt is another common Japanese maple disease. It is a soil dwelling fungus with symptoms that include yellowing leaves that fall prematurely. It sometimes affects only one side of the tree, leaving the other looking healthy and normal. Sap wood may also become discolored.

Moist, sunken bruising on leaves is a sign of anthracnose. The leaves eventually rot and fall. Again, mature Japanese maple trees will probably recover but young trees may not.

Proper annual pruning, cleaning up of fallen leaves and twigs, and yearly replacement of mulch will help prevent the infection and spread of these Japanese maple tree diseases.

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Factsheet | HGIC 1016 | Updated: Nov 16, 2013 | Print

Japanese maple (Acer palmatum) in full fall color.
Joey Williamson, ©HGIC, Clemson Extension

Maples (Acer species) are deciduous trees (sometimes shrubs) often grown for the shade they produce and their exceptional autumn color. They may be narrow and columnar, wide spreading and round-headed or low and mounded. Red maple (Acer rubrum), Japanese maple (A. palmatum), southern sugar maple (A. barbatum) and chalkbark maple (A. leucoderme) are adapted to all areas of South Carolina. Generally, sugar maple (A. saccharum), Amur maple (A. ginnala) and paperbark maple (A. griseum) are not suited to the Coastal Plains.

Powdery Mildew

As its name suggests, powdery mildew appears as a powder-like growth on leaves, buds and stems. It causes leaves to twist, curl and distort. Powdery mildew is caused by a fungus that spreads quickly and doesn’t need moisture to grow. It is prevalent in moderate temperatures and shaded areas. Neem and horticultural oil are two fungicides that can help control the powdery mildew attacking the Japanese maple. In addition to fungicide application, keep the ground near the tree free of organic litter to prevent the spread of the fungal disease.

Pruning Japanese Maples

Of all the Japanese maple problems dead branches can be one f the most alarming. An annual pruning of Japanese maple trees and shrubs to remove dead or dying branches and to keep the tree's shape is recommended over the cooler winter months. But if a tree or shrub is severely affected by a fungus, cutting off any limbs that appear diseased or dying -- rather than just the leaves appearing infected -- may be necessary to save the plant.

Thinning out any tightly grouped stems is also important this allows better air circulation and light penetration to encourage the health of the tree or shrub. This should be done mid-spring, after leaf buds have erupted and the fungal attack can be verified. All limbs, sticks and twigs should be removed from around the tree or shrub and burned to eliminate the fungus as soon as possible in the early part of the growing season.

Acer palmatum 'Osakazuki'

This Japanese Maple has excellent fall color and resists leaf scorch in the sun. The best leaf color is in partial shade. It has a rounded form and grows 15 feet to 24 feet tall.

They prefer rich, moist, acidic soil, but are adaptable to clay and sandy soils. Keep watered during dry spells to keep it looking its best.

Use this small tree as a specimen, foundation planting, or in an Asian garden. It does well as an understory tree in the dappled shade of a woodland garden and tolerates being planted with needled evergreens.

Propagate it by softwood cuttings or grafting.

Insects, Diseases, and Other Plant Problems: Aphids and horse chestnut scale are occasional problems. It may be affected by verticillium wilt.

VIDEO Created by Elizabeth Meyer for "Trees, Shrubs and Conifers" a plant identification course offered in partnership with Longwood Gardens.

Profile Video: See this plant in the following landscape: Cultivars / Varieties: Tags: #fall color#small tree#drought tolerant#interesting bark#specimen#low maintenance#winter interest#fall interest#cottage garden#wind tolerant#asian garden#fall color red#fall color orange

Summer form TeunSpaans CC BY-SA 3.0 Fall form Jean-Pol GRANDMONT CC BY-SA 3.0 Leaves in the summer. Kathleen Moore CC BY 2.0 Leaves TeunSpaans CC BY-SA 3.0 Fall leaves Sten Porse CC BY-SA 3.0 Bark Kathleen Moore CC BY 2.0 Trunk TeunSpaans CC BY-SA 3.0 Samara Jean-Pol GRANDMONT CC BY-SA 3.0

Red Dragon Japanese Maple Care

You might have admired mature Japanese red maples with their branches cascading to the ground. Be aware, however, that it takes many years for the tree to look like that. This is not to say that a young Red Dragon Japanese maple is not attractive, as the foliage is just as stunning no matter what the tree’s age.

Red Dragon Japanese maple is a slow grower and not pruning it and letting nature takes its course is part of the charm.

When planting, the roots need to be spread out to discourage the circular growth habit. Aim the roots outwards so they do not strangle themselves, which is common in many maples.

If you have a black walnut tree in your yard, you can plant a Red Dragon Japanese maple without concerns because Japanese maples are tolerant of black walnuts.


It is best to plant Red Dragon Japanese maple where it gets morning sun and afternoon shade.

A location where it is protected from the midday sun by a fence or a building is a good option. Another option is to plant it as an understory tree, so it grows in the dappled shade of a large deciduous tree with an open canopy.

The leaves of the laceleaf maples are very thin and delicate and too much hot, direct sun will scorch them.

The soil needs to be evenly moist, well-drained, and rich in organic matter. Japanese maple does best in soil that is slightly acidic. If your garden soil is alkaline (measure your pH if you are unsure), add chelated iron to the soil once a year, which you can find at garden centers.


After planting the tree, water it regularly for the first two growing seasons, until it is established.

Red Dragon Japanese maple, like all maples, has shallow roots, so, unlike other trees, their roots won’t reach deep into the soil to get water. It also means that the roots are exposed to the elements and dry out quickly. Therefore it is important to mulch around the tree to retain the moisture, and water the tree during dry spells.

Temperature and Humidity

Red Dragon Japanese maple can withstand moderate humidity, but the tree does not do well in hot weather above 90 degrees F. Hot dry wind can be especially damaging to the tender leaves and scorch them.

Similarly, in windy locations, the tree can suffer winter damage from chilly gusts, so pick a spot that offers protection.

The tree tends to leaf out early, which, in the event of a late frost, can also damage the young leaves.


When planted in rich soil with plenty of organic matter, Red Dragon Japanese maple does not need a lot of fertilizer. If the soil needs a nutrient boost, in late winter or early spring, apply slow-release or controlled-release fertilizer pellets.

Do not use liquid fertilizer because it will make the tree grow too much foliage too fast, which is counter to its nature, and that can lead to breakage. A fertilizer that is high in nitrogen is not good for the same reason.

You can propagate a Japanese maple through seeds and softwood cuttings. The different cultivars are also grafted onto rootstock.

Aside from their use in bonsai, dwarf Japanese maples can also be grown as traditional container trees and moved about the yard throughout the season. Plant them in a container with adequate drainage holes, because Japanese maples don't like to have their roots sitting in water. A high-quality potting soil is just fine as long as it's one that drains well.

Watch the video: Training Japanese Maples To Grow Properly