Canker on Dogwood: Causes, Different Types & Management

As you take a relaxing walk in your garden, sipping on a steaming cup of coffee, you happen to notice that your cherished dogwood tree seems to be ailing.

Upon closer inspection, you notice sunken, discolored patches on the bark — a telltale sign of canker disease. Your heart sinks.

Don’t despair! Armed with the right knowledge, you can wage a successful battle against this common tree ailment.

To treat canker on dogwood, start by pruning and disposing of all infected branches to reduce the spread of the disease. Improve air circulation around the tree by pruning, as this can help reduce the conditions that favor the disease. If necessary, apply a fungicide labeled for the control of canker diseases.

In the following, we’ll explain all about canker diseases in dogwood trees, exploring their causes, life cycle, the conditions that favor their development, and the impact on tree health and appearance.

We’ll also provide a detailed guide on the symptoms and diagnosis of these diseases and comprehensive management strategies.

So, whether you’re currently dealing with these diseases or just want to be prepared, read on for a wealth of information.

Diagnosing and treating common dogwood problems yourself is possible. Learn how in my article, Dogwood Diseases and Pests.

Understanding Cankers on Dogwood Trees

Canker diseases are serious diseases that can significantly impact the health and appearance of dogwood trees. Understanding these diseases is the first step toward effective management and control.

What Are Cankers?

Cankers are localized, necrotic (dead) areas on the bark of a tree, often appearing as sunken or discolored patches.

They are typically caused by various types of fungi that infect the tree, causing the bark to die in that area.

Over time, the canker can girdle the branch or trunk, disrupting the flow of water and nutrients and leading to the death of the part of the tree above the canker.

Causes of Cankers

Cankers on dogwood trees can be caused by several different fungi, including species of the genera Phytophthora, Botryosphaeria, and others.

These fungi typically enter the tree through wounds or natural openings and infect the bark and underlying wood.

Conditions That Favor the Development and Spread of Cankers

Canker diseases are often more severe in trees that are stressed due to factors such as drought, poor nutrition, or other diseases. The fungi that cause cankers can also spread more rapidly in wet, cool conditions.

Proper care of dogwood trees, including appropriate watering, fertilization, and pruning, can help reduce the risk of canker diseases.

Impacts on Tree and Tree Prognosis

Canker diseases can have a significant impact on the health and appearance of dogwood trees. Infected trees may display sunken, discolored patches on the bark, branch dieback, and in severe cases, tree death.

The prognosis for a tree with a canker disease depends on the severity of the infection and the overall health of the tree.

If the disease is detected early and managed properly, it’s possible to control the disease and save the tree. However, in severe cases, the tree may decline and eventually die.

Crown Canker

Crown canker is a common disease that can affect dogwood trees. It’s caused by the fungus Phytophthora cactorum, which infects the crown of the tree, leading to the development of a canker.

Symptoms

• Cankers: Sunken, dark brown to black lesions or cankers at the base of the trunk near the soil line or on the lower branches may have a rough, cracked, or discolored surface. As the disease progresses, the cankers can expand and girdle the affected areas, leading to the decline and death of the tree.
• Bark discoloration: The bark around the cankers may show signs of discoloration, typically turning dark brown or black. This discoloration can extend beyond the cankered areas.
• Dieback: Crown canker can lead to the dieback of branches and foliage above the affected areas. The dieback may start at the tips of branches and progress inward, resulting in the decline of the tree’s overall health and vigor.
• Wilting and leaf yellowing: Infected trees may exhibit wilting or drooping of leaves as well as yellowing or browning of foliage. The leaves may show signs of chlorosis (yellowing) or necrosis (browning) and may eventually drop prematurely from the tree.
• Stunted growth and tree decline: Crown canker can weaken the tree and cause stunted growth, with reduced foliage, smaller leaves, and a generally unhealthy appearance. The tree’s overall vigor may decline over time.

Disease Cycle

The Phytophthora cactorum fungus survives in the soil and in infected plant material. It spreads through the soil water to infect the roots and crown of the tree.

Once inside the host, the fungus decays the bark and underlying wood, disrupting the tree’s ability to absorb water and nutrients.

Management Strategies

Managing crown canker involves a combination of cultural practices and, if necessary, fungicide applications.

• Sanitation: Remove and dispose of any infected material, including roots and stumps, to reduce the source of infection.
• Improving Soil Drainage: Since the fungus thrives in wet soil conditions, improving soil drainage can help reduce the risk of infection. This can be achieved by adding organic matter to the soil, creating raised beds, or installing a drainage system.
• Avoiding Overwatering: Overwatering can create wet soil conditions that favor the development of the disease. Water your dogwood trees appropriately, providing enough moisture for the tree’s needs but avoiding waterlogged conditions.
• Fungicides: Applying a fungicide labeled for control of Phytophthora diseases. Fungicides containing the active ingredient mefenoxam or metalaxyl can be effective against crown canker.

Golden Canker

Golden canker is a disease that specifically affects dogwood trees. It’s caused by the fungus Cryptodiaporthe corni, which infects the branches and trunk, leading to the development of a canker.

Symptoms

• Cankers: Distinct cankers on the trunk, branches, and twigs typically have a raised, blister-like appearance with a golden or orange-brown color. Over time, the cankers may enlarge and become sunken and discolored, often turning dark brown or black.
• Dieback: Infected branches and twigs may experience dieback, where they gradually decline, turn brown or black, and eventually die. The dieback usually starts at the tips of branches and progresses inward.
• Gumming: Golden canker can lead to the production of a sticky, amber-colored sap or gum that oozes from the cankers. This gumming may be visible around the edges or within the cankered areas.
• Bark discoloration: The bark surrounding the cankers may show signs of discoloration, often turning reddish-brown or bronze. This discoloration may extend beyond the cankered areas.
• Leaf wilt and defoliation: Infected branches may exhibit wilting or drooping of leaves. Leaves may turn yellow or brown, wilt, and prematurely drop from the tree. This can lead to defoliation and an overall weakened appearance of the tree.

Disease Cycle

The Cryptodiaporthe corni fungus survives in infected branches and cankers. It spreads through wind and rain splash to infect healthy parts of the tree or neighboring trees.

Once the fungus infects a host, it decays the bark and underlying wood, disrupting the flow of water and nutrients.

Management Strategies

Managing golden canker involves both cultural practices and fungicide applications.

• Sanitation: Prune and dispose of any infected branches to reduce the source of infection.
• Pruning: Prune to improve air circulation and reduce humidity around the tree. Also, prune out any diseased branches.
• Fungicides: Applying a fungicide labeled for control of canker diseases. Fungicides containing the active ingredient propiconazole can be effective against golden canker.

Anthracnose Canker

Anthracnose canker is a disease that can affect a wide range of trees and shrubs, including dogwoods.

It’s caused by several species of the fungus Discula that infect the branches and trunk, leading to the development of a canker.

Symptoms

• Cankers: Anthracnose canker causes sunken, irregularly shaped lesions or cankers on the trunk, branches, and twigs of dogwood trees. These cankers may be discolored, dark brown to black, and have a rough or cracked surface. They can expand and girdle the affected branches or trunk.
• Dieback: Infected branches and twigs may experience dieback, where they gradually decline, turn brown or black, and eventually die. The dieback typically begins at the tips of branches and progresses inward.
• Leaf spots: Dark brown to purple spots on the leaves of dogwood trees may have a target-like appearance with concentric rings. As the disease progresses, the spots may enlarge, merge together, and cause the leaves to wither and drop prematurely.
• Twig blight: In addition to cankers, anthracnose canker can cause the development of small, elongated, sunken lesions on the twigs. These lesions may girdle the twigs, resulting in twig blight and dieback.
• Defoliation: The combination of leaf spots and twig blight can lead to significant defoliation, where the tree loses a substantial portion of its foliage. This can weaken the tree and affect its overall health and vigor.

Disease Cycle

The Discula fungi survive in infected branches and cankers. They spread through wind and rain splash to infect healthy parts of the tree or neighboring trees.

Once the fungus infects a host, it decays the bark and underlying wood, disrupting the flow of water and nutrients.

Management Strategies

Managing anthracnose canker involves both cultural practices and the use of fungicides.

• Sanitation: Prune and dispose of any infected branches to reduce the source of infection.
• Pruning: Prune to improve air circulation and remove any diseased branches.
• Fungicides: Apply a fungicide labeled for control of anthracnose diseases. Fungicides containing the active ingredient chlorothalonil can be effective against anthracnose canker.

Botryosphaeria Canker

Botryosphaeria canker is a disease that can affect a wide range of trees and shrubs, including dogwoods.

It’s caused by several species of the fungus Botryosphaeria that infect the branches and trunk, leading to the development of a canker.

Symptoms

• Cankers: Botryosphaeria canker causes sunken, oval-shaped lesions or cankers on the trunk, branches, and twigs of dogwood trees. These cankers may appear discolored, dark brown to black, and may have a rough or cracked surface.
• Dieback: Infected branches and twigs may exhibit dieback, where they gradually decline, turn brown or black, and eventually die. The dieback usually starts at the tips of branches and progresses inward.
• Gumming: The presence of a dark, sticky sap or gum oozing from the cankers is another symptom of Botryosphaeria canker. This gumming is often visible around the edges or within the cankered areas.
• Leaf discoloration and wilting: Leaves on infected branches may display discoloration, wilting, or browning. They may also exhibit marginal necrosis (browning or death of leaf edges) or develop a scorched appearance.
• Stunted growth: In severe cases, the overall growth of the tree may be stunted. Infected trees may show reduced vigor, with smaller leaves, sparse foliage, and a generally weakened appearance.

Disease Cycle

The Botryosphaeria fungi survive in infected branches and cankers. They spread through wind and rain splash to infect healthy parts of the tree or neighboring trees.

Once the fungus infects a host, it decays the bark and underlying wood, disrupting the flow of water and nutrients.

Management Strategies

Managing Botryosphaeria canker involves sanitation, pruning, and fungicide treatments.

• Sanitation: Prune and dispose of any infected branches to reduce the source of infection.
• Pruning: Prune to improve air circulation and reduce humidity around the tree. Also, prune out any diseased branches.
• Fungicides: Apply a fungicide labeled for control of Botryosphaeria diseases. Fungicides containing the active ingredient propiconazole can be effective against Botryosphaeria canker.

Prevention Strategies

Preventing canker diseases involves maintaining the overall health of the tree and modifying the environment to make it less favorable for the disease.

This includes proper watering and fertilization, avoiding overwatering, and planting in a location with good air circulation and sunlight.

Also, consider planting disease-resistant varieties of dogwood if possible.

Related Questions:

Does Canker Spread From Tree to Tree?

Yes, the fungi that cause canker diseases can spread from tree to tree. They can be spread by wind and rain splash as well as through the movement of infected plant material.

Therefore, it’s important to practice good sanitation, including the removal and disposal of infected branches, to prevent the spread of the disease.

Can You Save a Tree With Canker?

The prognosis for a tree with a canker disease depends on the severity of the infection and the overall health of the tree.

If the disease is detected early and managed properly, it’s possible to control the disease and save the tree. However, in severe cases, the tree may decline and eventually die.

Closing Thoughts

Canker diseases are a significant threat to dogwood trees, but with knowledge of the diseases and their management, you can take steps to protect your trees and maintain their beauty and health.

Remember that the key to managing canker diseases lies in early detection, appropriate treatment, and preventative measures. With these strategies, you can enjoy the beauty of your dogwood trees for many years to come.

If you enjoyed this article and would like to learn more, I recommend reading these as well:

• Dogwood Anthracnose: Symptoms, Impacts & Control Methods
• Dogwood Root Rot: Causes, Identifying, Treating & Preventing