How To Remove Fungus From Japanese Maple Trunk

Japanese maples are the kinds of trees that grow well almost everywhere. But when the winter season arrives, the cool and wet weather can cause various fungal infections on this beautiful tree. 

Imagine you have a gorgeous Japanese maple and one day they have suddenly turned ugly and unsightly. And trust me, this is not just about the appearance of the tree. You see, if you don’t start to treat your Japanese maple right away, it will soon be a disaster.

Because if you leave the tree untreated it will become very weak and gradually succumb to untimely death. But we won’t let that happen. Because with proper care your Japanese maple will restore its beauty and health in no time.

However, this will only happen if the right actions are taken at the right time. And the good news is, you don’t have to get worked up about it. Because in this article we have prepared an ultimate guide for you to get rid of the fungus from the trunk of your Japanese maple with all the tips and tricks.

So, without making any delay, let’s get the things underway–

 Why Are There Fungus On the Japanese Maple Tree?

1. Powdery Mildew On Japanese Maple

Powdery mildew is caused by a fungus that attacks the Japanese maples very frequently. Powdery mildew can be noticed very easily because it covers the leaves with a white powdery substance. And it looks as if someone dusted powder over them.

Though mostly it covers only the upper side of the leaves. However, when the infection isn’t treated in a timely manner it reaches the trunks of the Japanese maple. As a result, the trunk gets white powdery patches all over the surface and the tree looks very ugly and unattractive.

Anyway, this fungal disease does not directly kill the Japanese maple trees. But it surely makes them unbelievably sick and weak. As a result, the tree becomes susceptible to many other pests and diseases.

So basically it’s best to get rid of the disease before it brings more problems that could be even fatal for your Japanese maple trees.

What Causes The Powdery Mildew?

Powdery mildew can be caused by many kinds of fungus such as Erysiphe, Podosphaera, etc. But the most common fungus that attacks the Japanese maples is Phyllactinia marissallii.

Powdery mildew is a very troublesome disease, especially in areas with high rainfall. This fungus doesn’t usually attack unless the environment isn’t favorable for the infection. And the conditions are hot and humid weather with poor air circulation around the plants.

The powdery mildew fungus prefers warm days and cold nights with a temperature around 68° to 86°F. When the temperature is higher than 90°F the fungal spores cannot germinate and get killed.

This disease will occur more if the Japanese maple is shaded or under low light intensity with a relative humidity greater than 90%.

Powdery mildew spreads very fast because the spores don’t even need an external water source like another fungus to spread around other plants. Even more surprisingly, the spores are killed under strong rainfall.  So, the spores mostly travel by air to the neighboring plants.

However, the fungus does not easily go away. It survives even in the absence of host tissues. The spores stay dormant and get active when they find a favorable environment.

Follow the ultimate A-Z guide on the management of powdery mildew not only just for your Japanese maple but also for all other plants–

How To Get Rid Of The Powdery Mildew From The Japanese Maples?

First off, you have to make sure your Japanese maple isn’t in a shaded condition. Since you cannot move an established tree, you have to make sure other plants are not crowding it.

And if the tree has dense foliage then trim back a little. Also, thin out the stems that are very closely grouped with one another. This will be helpful to ensure proper sunlight penetration and airflow throughout the tree.

It’s good to do an annual pruning every year to cut off all the dead and diseased branches. This will also ensure optimum growth of the tree. So you can see proper thinning and pruning will come a long way in preventing the powdery mildew from happening every spring season.

It’s very important to cut off the affected leaves and stems with powdery fungal spores. Immediately remove the affected leaves and branches by putting them in the polyethylene bags and throwing them in the waste bin. 

Because if you leave them on the ground the spores will survive and again attack other trees and shrubs. And trust me, If this happens it will be even more difficult to get rid of the disease than the previous occurrence. 

So, to get rid of the powdery mildew, you need to apply a good fungicide that will not only eradicate the current mildew spores but also will provide protection from the disease in the future.(Our Pick: Bonide 811 Copper 4E Fungicide)

When you use the fungicide carefully follow the label about the instructions on how to apply it. Because if you apply the fungicide incorrectly you can end up killing your tree. Also, you have to repeat the application at a certain interval usually after two weeks. 

Another important thing is that you have to protect the maple that is infected with the powdery mildew and has become weak. You have to take good care of the tree and for this, you can apply a balanced fertilizer during the spring. So that your Japanese maples can get all the nutrition they need and get strong. Because a healthy tree can fight against this fungal disease more easily.

Try these simple homemade fungicide recipes that will  also work as a supplementary action against the fungal spores:

#Recipe 1: Clove Oil Fungicide Recipe


  • 200 ml of clove oil
  • 200 ml of water
  • 2-3 teaspoons of liquid mild dish soap


  • Mix all the ingredients and pour the solution into the sprayer
  • Spray over the fungal spores thoroughly once every week until the problem is solved

#Recipe 2:- Baking Soda Fungicide Recipe


  • 1 tablespoon of baking soda
  • 2 teaspoons of liquid dish soap
  • 2 teaspoons of any cooking oil
  • 3 liters of water


  • Combine all the ingredients and pour it into the sprayer
  •  Spray on your tree up to twice a week for best results

Note: Before using the homemade recipes on your tree, be sure to check on a small portion first. If you think it’s working then spray the solution to the whole tree. If it doesn’t work then you can try to slightly change the amount of the ingredients. But be aware of the concentration because a high concentrated solution will burn your tree.

2. Sooty Mold On Japanese Maple

Sooty mold is a black-colored fungal spore that covers the leaves of your Japanese maple. However, when the infection is severe it can reach up to the trunk of the tree.

The mold looks dark grayish or black with a velvety appearance on the leaves and branches. Even though the mold doesn’t kill the maple tree, it brings about other serious problems for the tree.

For instance, Because of sooty mold, most of the leaves get covered and as a result, sunlight fails to penetrate into the tree. Consequently, the rate of photosynthesis drastically reduces.

And the tree becomes very weak and susceptible to many other fungal and bacterial diseases. Moreover, the tree looks extremely ugly and dirty because of this black mold.

What Causes The Sooty Mold?

The fungus mainly grows on a sticky substance called honeydew which is a sweet and sticky substance. And this liquid is secreted by sap-sucking small insects like aphids, whiteflies, leafhoppers, mealybugs, psyllids, etc.

Honeydew sticks to the plant surface and black mold grows over it. The leaves that are coated with sooty mold fail to make food and prematurely drop off.

How To Get Rid Of The Sooty Mold From The Japanese Maples?

Since sooty mold is brought by the small sap-sucking insects, our main target is to prevent them from secreting honeydew and get rid of them for good.

Constant checking is a necessary step to keep up to date with any insect infestation. Whenever you see the listed pests you have to control the population with a good insecticide.  Be sure to pick one that’s not going to kill the insects that are beneficial for us (our pick: Natria 706250A Neem Oil Spray for Plants Pest Organic Disease Control)

Besides that, you have to feed the tree with a balanced fertilizer and water it properly so that your Japanese maple is healthy. The next step is to prune off the branches that are severely coated by the black mold. 

Also, encourage predator insects in the area so that the pest populations will naturally stay in control. Once you get rid of the pests the mold growth will gradually reduce over time. Then you can wash the remaining sooty mold off your tree with a strong stream of soapy water.

Control the pests with the following homemade fungicide recipes that are highly proven effective:

#Recipe 1:- Horticultural Oil Recipe


  • 3 teaspoons of liquid mild  dish soap 
  • 250 ml of any cooking oil 


  • Mix the oil and soap and pour in an airtight bottle
  • Take 4 tablespoons of the solution and mix with a liter of water
  • Spray  on both sides of your Japanese maple leaves 
  • Make sure the insecticide reaches the underside of the leaves very well
  • Repeat every week

#Recipe 2:- Neem Oil Recipe


  • 2 tablespoons of neem oil 
  • A gallon  of water


  • Mix the ingredients and spray in your Japanese maple tree
  • The neem oil is very effective in killing the pests that cause sooty mold
  • So keep repeatedly spraying this solution on your tree every week until the sooty mold is eliminated
  • As a precautionary measure, spray every 2 weeks even after the mold has gone

 Frequently Asked Questions (FAQs)

What does fungus look like on a Japanese maple?

You will either see white or gray substance over the leaf surfaces. Other than that, the leaves will turn yellow and become droopy. In some cases, the leaves will prematurely fall resulting in complete defoliation of the Japanese maple.

How do I know if my Japanese maple is dying?

You have to cut a small piece of the dead bark with a sharp knife. Then inspect the underside of the bark. If it looks green that means the tissue is still alive and the tree will gradually recover. But if the part is dry and brownish in color then that part of the tree is dying.

Can you bring a Japanese maple back to life?

If the tree is already dead then there’s no way to save it back to life. But if you find the woody part underneath the bark is still alive then you have to take proper care and water it regularly. Soon it will re-establish itself beautifully.


Japanese maples aren’t troublesome at all. They easily adjust to the environment and require a very little amount of your time. But to battle the fungal infections they need some aid and treatment. 

Don’t let powdery mildew and sooty mold fungus destroy the trunk of your Japanese maple. Just take a few timely measures and your tree will be as good as new.

In this article, I have discussed how to solve the fungal problems on your Japanese maple trunk in detail.  Yet do you want to know the best part?  You can follow the same control measure for eliminating the other fungal problems that occur in your Japanese maples like verticillium wilt, anthracnose, and many other diseases.

Leave a Comment