Powdery Mildew on Japanese Maple Leaves – Remove it Forever 

It is undoubtedly disappointing to see powdery mildew on Japanese maple plants. A beautiful Japanese maple plant is also inside my yard where sometimes I see a growth of powdery mildew disease. 

Meanwhile, I am familiar with the causes behind this problem and they are- shady conditions, high humidity, moderate temperature, extreme airspeed, overwatering and most importantly the season favorable for the existence of the disease. 

Due to the fungal growth, this disease is established. If you prefer, you can have a look at the causes responsible for this disease and their solution in a short range.

Shady condition Plants should be kept in bright sunlight and afternoon shade
High humidity The humidity level should be between 60-70%
Moderate temperature The temperature should be between 52-55°F
Extreme air speedKeep your plant covered to avoid spore spreading or use a heavy water stream and avoid close plantation 
Overwatering Provide water to your plant as its a necessity 
SeasonTake extra care of your plant 

How to Identify Powdery Mildew on Japanese Maple?

Before describing the causes and their solution, I want to highlight the appearance of this notorious problem. If you can see any white powdery spot on the upperside of the leaves, you can be sure of powdery mildew. 

The powdery elements may adhere to the nails sometimes. In the case of severe infestation, the powdery mass covers almost all the parts of the leaves and the leaves look dusty colors.

6 Causes of Powdery Mildew Attack in Japanese Maple Plants

1. Shady Condition

Shade is one of the main problems of Japanese maple plants. The fungus cannot grow in bright sunlight. But whenever they get enough shade, their spores become alive and get a proper environment for spreading. Thus they start to spread and this disease infestation grows much. 

Control Measures

Try to keep your plant in such a place where it can get enough light. The light should be bright and the plant should be exposed to the light. At least 6-8 hours of sunlight is necessary to prevent powdery mildew. 

But make sure that your plant is getting enough afternoon partial shade. Otherwise, it will initiate leaf scorching as maple plants cannot carry on their leaf mechanism properly in continuous bright light for many hours.

2. High Humidity

Excessive humidity is the most preferable condition for growing powdery mildew. The cloudy condition helps to grow them fast due to their nature. The spore-producing, germinating, and whole life cycle of the fungus are continued best in such a high-humidity environment. 

Control Measures

Always keep the humidity level between 60-70%. The watering procedure regulates the humidity level. So make sure of perfect watering. In the case of cloudy days, you can use a few drops of liquid soap solution to prevent the fungus growth.

3. Moderate Temperature

Next, the temperature issue is another burning issue for the growth of fungus. They love to grow in moderate temperatures of 68-80°F. If you keep your plant at such a temperature, the plant will be susceptible to the disease and the fungus growth will be at a high range.

Control Measures

Powdery mildew cannot occur at too low temperature or too high temperature. Again, the excessive temperature is detrimental to the maple plant. Hence, try to maintain a low temperature during planting and during the young period until the plant gets self-protection.

4. Favorable Season

This is an inevitable issue for the growing of powdery mildew. The fungus grows better in late spring or early summer. Environmental conditions like humidity and temperature range are preferable for fungus reproduction. That’s why planting Japanese maple should be prohibited at that time.

Control Measures

You should not plant a Japanese maple in late spring. Provide liquid soap solutions to prevent the growth of the fungus once a month in spring and summer. 

Take intensive care of your plant so that it can get strength and create resistance against the disease. Make sure that any type of wound is not made in your plant. Otherwise, the fungus will enter through the wounds.

5. Extreme Air Speed

Stormy air is the most powerful thing for spreading the spores of the fungus responsible for powdery mildew.  As it is considered an air-borne disease, the spores are too light to spread with air.

If there is any high-speed air or stormy air, the nearby plants also get affected by the spreading of the spores. They continue their life cycle in the new plants and grow in the new plants.

Control Measures

Avoid planting at a closed distance. Maintain the appropriate spacing between two plants. Else, you can also cover the plant with polythene in the case of a storm or other problems.

6. Overwatering

The last phase of this problem chart is overwatering which may also increase the infestation by facilitating spore production. The fungus of powdery mildew loves humid conditions. 

If you overwater your plant, the fungus can easily grow in the root zone due to the soaked conditions. Thus, they continue their reproductive cycle and produce more and more fungi.

Control Measures

Japanese maple plants don’t need excessive amounts of water. You should water them as their necessity. As they grow better in the winter season, the need for water is low for them. 

That’s why you have to water the plant in the case of a dry period. At the same time, the drainage system should also be perfect and well-furnished.

How to Protect Japanese Maple Plants From Powdery Mildew Infestation

To protect your Japanese maple plants from powdery mildew infestation, you can follow the below-mentioned steps-

  • Pruning

Pruning is the procedure of removing the affected plant parts to destroy the spreading mechanism of the fungus. It will help your plant in two ways- firstly, the fungus won’t be able to spread anymore. And lastly, the plant will produce new leaves with a fresh look.

  • Microclimate Manipulation

This is mainly the process of maintaining all the necessary elements of the plant in a perfect manner. Japanese maple plants need specific temperatures, humidity, sunlight, and watering conditions that I have mentioned already. 

To protect your plant, you have to make all these points perfectly available for the plant. At the same time, try to save your plant from any type of wound. Thus, they will be stronger from the inside and create resistance against the fungus.

  • Chemical Control

Here, I will inform you about the chemicals that you can use in your plant to remove the infestation. Fungicides under the carbendazim group can help you in this case satisfactorily. If they are available to you, you can spray them in your plant according to the labeled instructions. 

Here I can direct you to a new solution. As powdery mildew is not a severe disease, you can use homemade recipes also to remove them from your plant. Check some effective homemade solutions from here-

  • Potassium bicarbonate

Potassium bicarbonate is an extraordinary remedy for powdery mildew. Take 1 quart of concentrated or solid potassium bicarbonate to 16 quarts of water and dilute perfectly. Then, spray the plant.

  • Baking Soda Solution

Mix 2 tablespoons of baking soda and 2 tablespoons of vegetable oil in 1 gallon of water and spray it after diluting perfectly. 

  • Milk Solution

Take milk and water at a 1:10 ratio and mix them properly by stirring. Apply it to the infected parts or you may pour it into the soil.

  • Neem Oil

Neem oil solution is one of the most preferable homemade remedies for most gardeners. To prepare it, take 2 tablespoons of concentrated neem oil, 1 tablespoon of liquid soap, a few drops of essential oil, and ½ tablespoon of aloe vera powder in 1 gallon of water and mix it for spraying. (Our pick: Monterey LG 6145 70% Neem Oil Ready-To-Spray Insecticide, Miticide, & Fungicide)

 Quick Caring Suggestions for Japanese Maple Plant

SoilSandy loam and slightly acidic soil mixture consisting of perlite, coco peat, and sphagnum moss.
Sunlight Bright sunlight with enough afternoon shade
Temperature 52-55°F temperature is comfortable for them
Humidity Maintain humidity range between 60-70%
WateringWatering should be done when needed

If you are confused about the factor, you can check the caring rules from this video-


Which is the best season for growing Japanese maple plants?

It’s about fall when your Japanese maple plant will be able to thrive. As they love cool weather, the plant gets perfect environmental assistance for growth and development. 

Can powdery mildew kill the plant?

No. Powdery mildew is not as severe as other fungal diseases. Being a mild disease, hopefully, it will not kill your plant. It destroys the beauty of the plant due to its dusty and powdery whitish structure. 

Can powdery mildew be removed forever?

Yeah! If you can take care of your plant intensively, you may remove this fungus forever from your plant. But you have to make sure that the plant is in an environment where this fungus cannot grow again. 

Final Words

Gradually, I  reached the final destination of my article on powdery mildew on Japanese maple plants. Powdery mildew is mainly devastating for the beautification of the plant. Like other fungi or bacteria, they don’t affect the plant system much. 

But, the maple tree is a symbol of beauty for us. This is why we need to be concerned to save the beauty and to keep the life cycle or metabolism system of the tree undisturbed. 

In the case of finding it applicable or helpful, you can pick any type of suggestion that you need to keep your plant free from powdery mildew. Hopefully, you will get a clean and powdery mildew-free tree.

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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