Protecting Your Maple Trees: A Guide to Identifying and Treating Bark Diseases

Protecting Your Maple Trees: A Guide to Identifying and Treating Bark Diseases

With its smooth bark that develops interesting textures as it ages, the bark of maple trees, known as Acer bark, is a beautiful feature often overlooked. However, just like any other part of a tree, the bark can be vulnerable to various diseases and afflictions. In this guide, we will explore how to identify and treat common maple bark diseases, as well as how to prevent them from occurring. Let’s dive in!

Burr Knots and Galls

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Burr knots and galls are two common issues that can affect the bark of maple trees. Burr knots are small lumps that form from adventitious roots or bud tissues. They tend to grow larger and more knotted as the tree matures. While they may not be aesthetically pleasing, burr knots are actually valued by woodworkers for their unique swirls and patterns. On the other hand, galls are often caused by bacteria or infectious material left behind by pests. They can range in size and appearance, but they generally block the flow of nutrients and compromise plant growth.

To prevent burr knots, it is important to keep the trunk dry and avoid growing vegetation under the canopy. If you already have burr knots, you can remove them if there are only a few. Galls can be prevented by avoiding injuries to the tree and managing pests. If galls are already present, they can be cut out, but if the tree is severely affected, it may need to be removed.


Cankers are open wounds that become infected by fungal or bacterial pathogens. They often appear as sunken, irregularly-shaped lesions on branches or trunks and can cause various problems in the foliage, such as stunted growth and discoloration. Cankers can also clog the tree’s vascular system, leading to wilt and branch dieback. Avoiding environmental stresses and injuries can help prevent cankers.

Frost Damage

Extreme temperature changes, especially sudden drops in temperature, can cause frost damage to maple trees. When the bark and underlying wood contract at different rates, the bark can split, leaving the tree vulnerable to infections. Choosing suitable maple species for your local climate and providing lightweight coverings during cold spells can help prevent frost damage.


Lichens are unique organisms composed of fungi and algae or cyanobacteria that exist in a symbiotic relationship. They can be found on the bark of trees and are often indicators of good air quality. While they can grow on both healthy and unhealthy trees, addressing any health issues that may compromise the tree’s leaves can help control their growth.

Physical Damage

Maple trees can also be damaged by external factors such as lightning strikes, severe winds, and animal damage. Pruning damaged branches and treating bark injuries can help the tree recover.


Sapstreak is a fatal disease primarily affecting sugar maple trees. It is caused by a fungus that enters wounds in the tree’s trunk or root system. Prevention is crucial for sapstreak, as there is no known cure. Avoiding wounds and removing infected trees can help prevent the spread of the disease.

Sooty Bark Disease

Sooty bark disease is caused by a fungal pathogen that infiltrates and kills smaller branches before spreading to the trunk. It produces dark, sooty-looking masses under the bark and can eventually lead to the death of infected maples. Avoiding pruning during dry summer conditions and removing infected trees can help prevent the spread of the disease.


Sunscald occurs when high temperatures and harsh sun exposure cause severe bark damage, mainly in young trees. Using light-colored materials to cover the trunks can help protect them from the sun’s rays. Mulching properly is also essential to prevent moisture buildup and overheating.

In conclusion, understanding how to identify and treat common maple bark diseases is crucial for maintaining the health and beauty of your trees. By implementing preventive measures and addressing issues promptly, you can ensure that your maple trees thrive for years to come. For more information on tree planting and care, visit Tips Tree Planting. Happy gardening!

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