8 Common Japanese Maple Diseases (With Pictures)

The further the selection of plants goes, the more delicate they become. Therefore, lovers of ornamental plants constantly have to deal with various difficulties.

To treat the fungus on a Japanese maple, remove any dead or badly damaged leaves and spray the tree with an aqueous solution of multi-purpose fungicide. Also, provide good air exchange around the Japanese Maple and avoid overwatering.

These are general recommendations that work in most cases. Next, we’ll go into more detail about the most common Japanese Maple fungal diseases and how to deal with them.

I also highly recommend that you read the article Growing and Caring for Japanese Maple. There you will find a lot of useful information about these wonderful trees.

Disease	Symptoms	Treatment
Verticillium wilt	Blackening of the bark.	Spray wounds after pruning with fungicide.
Powdery mildew	White powder on the leaves.	Spray the leaves with horticultural oil.
Pseudomonas	Black branches.	Cut back the branch below the site of the pathogen damage.
Sooty Mold	Black spots on the leaves.	Spray the leaves with a multi-purpose fungicide.
Anthracnose	Brown spots on the leaves.	Spray the leaves with a copper fungicide.
Phyllosticta leaf spot	Brown spots on the leaves.	Spray the leaves with triazole fungicide.
Phytophthora Root Rot	Browning of the leaves.	Plant Japanese maple only in well-drained soil.
Tar spot	Black spots on the leaves.	Spray the leaves with a multi-purpose fungicide.

Verticillium wilt

Verticillium wilt is a serious disease that is not well treated. The pathogens of this disease enter through cracks in the bark or through wounds. Nematodes play an important role in its spread.

Once the disease enters the interior of the maple it begins to destroy the tissues that supply water higher up the branch. As a result, leaf petioles and leaves droop.

On branches where the disease has spread heavily, the bark turns black.

Treatment:

• Avoid unnecessary damage to the trunk and branches of Japanese Maple.
• Prune branches a few inches below the blackened area.
• Use only sterile tools for pruning. Clean the tools with rubbing alcohol for each tree.
• Spray wounds after pruning with multipurpose fungicide or copper fungicide.
• Allow free air movement around the maple tree.

Powdery mildew

Powdery mildew is one of the most common diseases not only among Japanese maples but also among most plants. Fortunately, this fungus is not as serious as the previous one.

The symptoms of powdery mildew are the blackening of the leaves and then they become covered with a white coat. Over time, the leaves will shrivel up and fall off.

Treatment:

• Remove badly damaged leaves.
• Improve crown ventilation by pruning some of the branches.
• Avoid overwatering and excessive humidity around the maple.
• Spray the leaves with a fungicide designed to fight this disease.
• Avoid using Neem Oil as it can damage the delicate leaves of the Japanese Maple.

Pseudomonas

Pseudomonas is another fungal disease that affects Japanese Maples. It usually occurs in late winter or early spring.

The pathogens enter through frost-damaged buds. At this point, the blackening of the branch occurs and the upper part of the branch dies off. If the leaves have already appeared, they also dry out and die off.

In most cases, the lower part of the crown remains intact. Most susceptible to this disease are 1-2-year-old branches.

Treatment:

• Cut back the branch below the site of the pathogen damage.
• Use a sterile and sharp pruning tool.
• After pruning, thoroughly spray the entire Japanese Maple with a product called Phyton 35.
• Avoid planting the maple in damp areas with poor ventilation.
• If possible, protect the maple from freezing winds over the winter.

Sooty Mold

Sooty mold is a fungal disease that develops on the sticky secretions of aphids. Aphids parasitize on the upper leaves and leave sticky secretions that fall on the lower leaves.

This is an ideal environment for this kind of pathogen. Next, the leaves affected by the fungus turn black. But at the same time, the leaf remains alive because the food of the fungus is the secretions and not the leaf.

Treatment:

• Wash off the aphids and black leaves with water from a hose.
• Remove badly damaged leaves.
• Aphids on Japanese Maple leaves can easily be controlled with insecticidal soap.
• Spray the leaves with a multi-purpose fungicide.

Anthracnose

The spores of this fungus settle on the leaves of the Japanese Maple and damage them. This disease is not capable of causing serious damage to the tree, but it can severely damage its aesthetic appearance.

The disease is most common in humid and low-wind conditions. Dark spots form on the leaves that turn brown and dry over time.

Sometimes the leaf may turn brown along the edge. Heavily damaged leaves will fall off.

Treatment:

• Clean the fallen leaves around the maple in the fall.
• Provide good air exchange around the maple.
• Do not overwater the Japanese Maple.
• Spray the leaves with copper fungicide. Repeat the spraying after 2 weeks.

Phyllosticta Leaf Spot

Phyllosticta is very similar to the previous disease because it causes leaf spots. The characteristic feature is that the spots can turn into small holes. If there are many holes, the leaf will die.

Usually, the spores of this fungus are found in plant debris on the ground. When wet and warm weather arrives, the spores become active. As a result, the leaves may be severely damaged but the tree will not suffer much.

Treatment:

• Keep the surface around the maple tree clean of leaves and other plant debris.
• Use well-drained soil for planting maple trees.
• Spray the leaves with triazole fungicide.
• Do not plant Japanese Maple in areas that are too dark and poorly ventilated.

Phytophthora Root Rot

Root rot is the most common disease of Japanese maple. It is a serious problem that should not be neglected.

It is usually caused by overwatering, poorly drained soil, or planting the maple in a wet location. As a result, the roots soften and experience oxygen deprivation.

The root system then begins to rot. The external symptoms are yellowing and falling leaves.

Treatment:

• Stop watering too often and water only if the soil is 1-2 inches dry.
• When planting, use well-drained soil.
• Do not plant Japanese Maple where water collects or stagnates.

Tar spot

This disease is not very serious and almost never leads to the death of the tree. However, it can ruin the aesthetic appearance of your maple tree.

When the warm season arrives, spores of the Rhytisma fungus begin to germinate on the leaves. At first, faint yellowish spots appear on the leaves, but over time they turn dark black. The spots resemble tar, hence the name.

Treatment:

• Each fall, collect fallen maple leaves and discard them far from your garden.
• If only a few leaves have spots, rip them off and discard them.
• If the infection is severe, spray the maple with a multi-purpose fungicide 2-3 times at monthly intervals.