How To Treat And Prevent Maple Tree Blight

Maples are among the most popular trees you can grow on your property and it’s not hard to see why. World-famous for their gorgeous fall foliage, the many varieties of maple trees add shade and curb appeal to your home all throughout the year.

Pile of Maple Trees Infected with Maple Tree Blight - Maple Tree Blight BlogThey’re also extremely versatile; there is a maple tree to fit the needs of practically any home. Japanese maples are excellent for smaller spaces as they grow easily in a compact environment. On the other hand, the famous sugar maple can grow to 75 feet high and 45 feet wide, an impressive size for any property.

Maples are also hardy trees, capable of handling a wide variety of conditions and growing in many types of soil and various lighting conditions. However, even the hardiest plants are subject to maple tree blight. Here’s what you can do about it:

What is Maple Tree Blight?

Blight simply refers to a disease that affects trees and other plants. It can have many causes, but in maple trees it’s usually due to a fungus, bacteria, or mildew.

The threat level that a blight poses depends a great deal on the overall health of the tree and the type of disease. At best, the problem is largely cosmetic and can be handled with a simple trim. At worst, the disease can choke the tree’s vascular system, rendering it impossible for it to receive water and vital nutrients. If this isn’t dealt with quickly, it can kill the tree.

Identifying Signs of Sickness

Among maple trees, there are several common diseases that you should learn to keep an eye out for. Knowing how to identify the various causes of maple tree blight will allow you to make the best decisions possible regarding the health of your trees. In many cases, signs of disease can be subtle at first. That’s why you should regularly conduct a thorough check of the leaves, roots, bark, and branches of your tree and take note of anything that seems unusual. Needless to say, it’s best to diagnose any potential illnesses and take steps to treat them as quickly as you can.

The Most Common Maple Diseases

There are a number of common causes of maple tree blight. Fungus, bacteria, and mildew are among the most common, although insects and weather conditions can sicken a tree as well. In many cases, you may notice signs of one disease that is somewhat harmless on its own, although it may be a sign of another, more dangerous condition in the tree.

Here are a few of the most common maple tree diseases:


Anthracnose is a common disease that affects the leaves of a maple tree. While it’s usually not truly harmful, it can do serious cosmetic damage to your tree and hamper your curb appeal. Signs of anthracnose include brown spots forming along the leaf veins, as well as leaf loss taking place too early in the year.

The disease is caused by a fungus that thrives in cold, wet conditions. Usually, this fungus starts to grow in fallen leaves during the winter and leads to a full-blown infection by mid-spring. Preventing this condition is usually as simple as keeping your tree and its leaves from sitting in stagnant, cool water. Rake up any fallen leaves during the fall and if you do notice any infected leaves, simply prune them as soon as you can.

Powdery Mildew

Another disease caused by a fungus, powdery mildew prefers hot and humid conditions and is most likely to strike during the summer. As its name suggests, powdery mildew makes leaves appear as if they are covered in powder, almost like they have been covered with flour.

The youngest leaves are usually the most affected by this disease; as the powdery mildew spreads, the leaves will curl up and turn brown as the fungus leaches away water and nutrients.

Preventing powdery mildew involves carefully pruning your maple trees; allowing plenty of room for air to circulate prevents the humidity that this disease thrives on. If you do notice signs of the disease, prune the affected leaves and make sure to destroy them far away from any other trees to prevent the fungus from spreading. You may also need to apply a fungicide to the leaves of your maple tree.

Tar Spot

Another common fungal disease, tar spot causes the leaves of your maple tree to develop black spots that look like tar. It’s another one that isn’t truly harmful to the tree, however, it affects the appearance of the tree enough to be worth concerning yourself over.

As a fungus, this disease also thrives in cool and humid conditions. There is very little you can do to prevent it other than raking up the leaves during the autumn. If your tree does develop tar spot, you can have the tree pruned and it should mostly take care of the problem.

Verticillium Wilt

This is a disease that’s a little more severe. If it’s left untreated it can lead to the death of your tree.

Verticillium wilt is caused by a fungus and is a challenging one to deal with as it’s hard to diagnose and cannot be cured. As it enters the tree, it will cause the leaves to discolor and shrivel up. Frequently, it affects the bark as well. As the fungus grows in the soil it can really only be handled by preventing its growth.

Watering your maple tree on a regular schedule and feeding the tree a low-nitrogen and high phosphorus fertilizer will help. If you have had other plants develop this disease and are concerned about the health of your maples, you can contact your local arborist and ask about solarization. This is a process that will heat up your soil enough to kill any fungi growing in it, however, it must be undertaken with care by a professional to avoid harming the tree.

Further Information

There are many other tree diseases that can lead to maple tree blight; depending on the conditions and overall health of the tree. In most cases, the disease can be prevented simply by keeping your trees as strong and healthy as possible.

Regular pruning, watering, and fertilizing will help with this. Proper conditions, such as the right soil and the correct amount of sunlight for any given tree species, will also help. And, of course, your tree should receive regular visits from an arborist; a professional tree doctor to diagnose, treat, and help prevent any illnesses. Mr. Tree is the best option if you are in the Portland area.

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