Japanese Maple Fungus Treatment – 7 Fungal Problems + Solutions

The Japanese maples mostly love to be in cooler temperatures but the problem is, this can bring about many fungal diseases on them because fungus naturally thrives in wet and cool weather. 

Initially, the fungus may not look dangerous but if they are not treated for a long time then it can even cause the death of your plant. And luckily if that doesn’t kill the plant it will obviously make their leaves black and yellow and their barks will have mold growth all over them.

As a result, your Japanese maple will look very ugly and unpresentable. However, with proper care, you can restore their beauty back.

In this article, I am going to point out what types of fungus can affect your Japanese maples and what are their distinctive features so you can figure out which one is causing problems in your tree. 

The good news is, for your convenience I’ve included one single ultimate treatment guide that will prove to be effective for any kind of fungal attack on your Japanese maple. 

So, let’s get into the details already–

What Kinds of Fungus Attack The Japanese Maples?

There are 7 different kinds of fungus that attack the Japanese maples so let’s list them out with their characteristics–

1. Verticillium wilt

Coming first, Verticillium wilt is a very serious fungal disease of the Japanese maples and it enters very easily through any cracks in the bark or open wounds. It’s basically a soil-borne disease and as it infects the Japanese maples, it quickly starts to destroy the internal tissues.

As a result, the water uptake of the plant is greatly hampered. Eventually, the leaves start to wilt and droop and even cause the bark to turn black. 

Here, the problem is that the verticillium wilt isn’t very easily detected and most of the time the fungus goes unnoticed and takes hold of the tree before the actual symptom arises. 

Since this can be a little tricky to diagnose as it does more harm in the root section that is not readily visible, here is a short video to help you get the whole picture of it to understand the wilt better–

2. Powdery mildew

Powdery mildew is one of the most common diseases of Japanese maple and it occurs very frequently but luckily this one is very easily detectable as well. Moreover, it’s not even that serious or deadly.

However, it will not take the life of your plant but it will weaken it to a great extent by suffocating the leaves with the powdery mold growth. As a result, other deadly fungal and bacterial diseases will easily attack your Japanese maple. This is why treating this one is as necessary as any other one. 

Usually, the infection begins with a white powdery substance that is laid down all over the leaves even on both sides and gradually the leaves start to curl and shrivel up and fall off at some point. 

3. Anthracnose

When the Japanese maples are affected by anthracnose, their leaves turn brown around the edges with circular black spots and in a severe case the leaves start to fall off. 

It usually occurs in humid and high-temperature conditions. Though this disease doesn’t cause fatal damage to the tree, it can cause some serious damage to the beauty of the tree. 

4. Pseudomonas Disease

This fungal disease appears in Japanese maples usually during the late winter or early spring season. The young branches aging a couple of years are the most susceptible ones to the attack of this fungus.

You see, when the frost causes some damage, it enters through those damaged places. The fungus starts to rot the branches and as a result, it blackens and dies off. If any leaves are infected they even dry out and fall off too. 

5. Sooty Mold

Sooty mold is a fungal disease but interestingly it grows over a sticky substance called honeydew that is secreted by aphids and other small insects. You see, Honeydew makes an ideal environment for the sooty mold to grow.

As a result of their attack, the surface of the leaves turns black and sticky and this prevents the leaves from doing much photosynthesis. Eventually, the Japanese maple lacks food and nutrition and turns very weak. 

6. Phytophthora Root Rot

This is the most common and one of the most devastating diseases of Japanese maple. In addition, this soil-borne disease is mainly caused by poor water drainage and overwatering issues. 

You see, it occurs when the root becomes suffocated in water for a long time and when it gets deprived of oxygen.

As a result, it starts to soften and rot. Externally, the leaves start to become yellow and eventually they fall off since the rotten roots cannot translocate enough food and water to them. 

7. Phyllosticta Disease

Phyllosticta isn’t a very common disease but it still occurs every once in a while in the Japanese maple tree. Moreover, it has a very distinct character of having leaf spots that gradually turn into holes. 

If the leaves have too many holes and are severely infected it can cause a quick and sudden death of the tree. The spores of this fungus are mostly found on ground debris and during wet and warm weather, the spores are spread through the water. 

How To Treat The Fungus On The Japanese Maple Trees?

1. Dispose of The Affected Leaves

First, we have to stop the fungus from spreading anymore. No matter what type of fungal attack it is, always get rid of the infected leaves at first. 

And whenever they fall off the tree, rake them up as soon as you can. This will remove the spores of fungus from your Japanese maple. 

Then you have to make sure you dispose of them completely. For this, you can either burn them or place them in a compost pit or you can also put them in a plastic wrap and throw it out in a garbage can. 

If you keep the leaves on the ground for a long time, the fungus will survive there in the winter and easily move and spread with air and water to attack the other healthy plants again in the spring. 

2. Use A Fungicide

If the fungus attacks the Japanese maples when they are very young, the plant can die from it because of being under too much stress. So it’s best to use a good fungicide that will keep the fungus away and kill off the existing ones as well. 

So, treat it with a fungicide that is very effective but non-toxic to your Japanese maple tree. Make sure you apply it before the trees are budding because the chemicals can cause the young buds to drop. (Our pick: Monterey LG 6145 70% Neem Oil Ready-To-Spray Insecticide, Miticide, & Fungicide)

Make sure you follow the label direction of the fungicide package very thoroughly and repeat the application after every two weeks unless the tree is totally cured from the fungus.

When applying it you can use a specialized sprayer to reach the big trees to make sure the application of the chemical is uniform on both sides of the leaves.

#Recipe 1:- Copper Spray Fungicide Recipe


  • A gallon of water
  • 50 mL of copper sulfate crystal
  • 150 mL of Calcium hydroxide (known as hydrated lime as well)


  • Take a plastic bucket and add some water and all of the hydrated lime in it and mix slowly with a plastic spatula 
  • Any metal buckets or spatula is not allowed because these can react with the ingredients and get corroded
  • While you are stirring start adding the copper sulfate crystals slowly into the bucket and continue to stir as long as it takes to mix
  • Now the fungicide is ready to be poured into the spray bottle
  • Shake this solution once in a while when you are spraying it on the Japanese maples because this solution keeps settling down easily
  • Spray carefully on both sides of your Japanese maples and over the open wounds
  • After using the fungicide discard the leftovers from the sprayer and wash it thoroughly because it can cause corrosion of the components
  • Don’t store it to use for next time, rather make a fresh batch every time

Caution: Before using this homemade copper fungicide in bulk in your Japanese maple, it’s better to use it on a small area of the leaf and see if the solution suits the plant. If there is an allergic reaction to the leaf then it’s probably best to leave this one out. 

3. Prune Off Some Leaves

Since the fungus thrives in wet and humid environments you have to make sure your Japanese maple has ample air circulation and light penetration throughout them. 

For this, you have to prune off the dead or dying branches. This yearly pruning will also help to keep the shape of the tree. 

Whenever you are pruning make sure the pruning shears are thoroughly sterilized with rubbing alcohol for every new tree otherwise these tools can also be another medium for the fungal spores to transfer to healthy trees. 

And thinning off the excessive branches will make sure your tree stays healthy and disease free all the time. However, the pruning needs to be done during the spring season with the utmost care. Because sometimes heavy pruning can send the tree into shock.

After that, spray some fungicide, preferably a copper fungicide on the wound so that it can protect the tree from any fungal spores from getting inside the tree through the open wounds. 

Besides, when you are pruning a blackened branch make sure you cut a few inches below that area just to be safe. After the pruning make sure to dispose of the branches, twigs and leaves right away.

4. Take Care Of Your Japanese Maple

To make sure the fungal diseases stay out of the way of your Japanese maples you need to take care of some more stuff. So, first off make sure the soil is well-drained and never waterlogged. 

Japanese maples prefer a bit cooler temperature so you can keep a layer of mulch around the tree to keep the soil moist and this will also help to keep the temperature of the soil down during the warmer seasons. 

However, sometimes the pests can harbor in the mulch materials so make sure you replace the mulch once or twice a year to prevent insect infestation. 

One of the most effective ways of controlling fungal diseases is that you have to look out for the watering making sure you don’t end up overwatering them. Try to water only when the top few inches of the surface of the soil is dry.

Also, try to avoid excessive humidity during the summer and chilly breezes during the winter as well around your Japanese maples. Plant them in a bright and sunny location with plenty of summer breeze.

Take care of the pest situation and if required use a good pesticide to get rid of the insects that secrete honeydew which could bring sooty mold into your maple tree.

You also have to keep the tree healthy because a healthy tree can handle any fungal attacks more efficiently and survive than any weak tree. For this, make sure you feed your plant a good dose of fertilizer that is specially made for shrubs and trees during the growing season.

 Frequently Asked Questions (FAQs)

Do Japanese maples need a lot of water?

At the initial stage, they need water every 3 days for a couple of months. After that, you can water them once every week depending on the soil condition. Again, if you feel the soil is drying out much sooner,  you can water it twice a week.

How long until the fungus goes away from the Japanese maples?

Normally it will take about a few weeks to completely recover. The time of the recovery will greatly depend on the type of fungus and the severity of the attack as well. Also the better kind of treatment they receive the more chance they have to recover faster

Can a Japanese maple take full sun?

Used as an ornamental tree, the Japanese maples are often planted in full sun. But this is not desirable for them. They actually prefer to be in partial shade condition. If they are planted in the full sun the leaves can get burned during the summer season.


Japanese maples are hardy enough to survive harsh environments but to battle against deadly fungal diseases, they come out a bit weak. And this is where your help is much needed. 

If you are able to maintain the hygiene of your landscape and be careful about watering, then half of your work will be done already. Other than that, help them to defend themselves against fungal attacks with the best fungicide that’s suitable for them.

I have tried to include all the information necessary and I hope you have found everything you need to know in this all-in-one fungus control guide and eliminated the fungal disease from your Japanese maples.

James Rivenburg
James Rivenburg
James Rivenburg

James Rivenburg is the founder of plantandpest.com, a passionate gardener with valuable experience and knowledge gained through trial and error. The website has a large community of followers who trust his tips and techniques and have succeeded with his advice. He is always Committed to helping others create a beautiful and healthy garden.

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