Blight and Dogwood Trees | Symptoms and Disease Treatment

Picture a flourishing and vigorous dogwood tree, its limbs adorned with stunning flowers, suddenly losing its allure due to an unknown illness.

This is the unfortunate reality for many gardeners dealing with dogwood blight, a disease that can rob these majestic trees of their beauty.

To treat dogwood blight, remove and destroy infected parts of the tree, improve air circulation by thinning the branches, and avoid overhead watering to reduce humidity around the tree. Fungicides containing chlorothalonil or mancozeb can be applied as a preventive measure during the growing season.

It’s not easy to watch a favorite tree suffer, but catching a problem in the early stages can increase the odds that your dogwood will survive.

Below, you’ll learn more about dogwood blight, including what causes it, how to prevent it, and how to manage it if it occurs.

Learn how to diagnose and treat common dogwood issues in my comprehensive article, Dogwood Diseases and Pests.

Understanding Dogwood Blight

Dogwood blight, also known as Discula blight, is a serious disease that can affect the health and aesthetics of dogwood trees. Understanding this disease is critical for effective management.

What Is Dogwood Blight?

Dogwood blight is a fungal disease caused by the pathogen Discula destructive.

It is also commonly referred to as anthracnose and primarily affects flowering dogwoods (Cornus florida), causing leaf spots, wilting, and premature leaf drop.

If left untreated, it can lead to significant defoliation and even death of the tree.

Life Cycle and Disease Transmission

The dogwood blight fungus overwinters in infected leaves and twigs on the ground. In spring, during wet weather, spores are produced and spread to healthy leaves by rain splash or wind.

Once the spores land on a susceptible host, they germinate and infect the tree, leading to the development of leaf spots.

Conditions That Favor Dogwood Tree Blight

Dogwood blight thrives in humid conditions and is more severe in shaded areas with poor air circulation.

Overcrowded trees or those under stress from drought, poor nutrition, or other diseases are more susceptible to infection.

Impacts on Tree & Tree Prognosis

Dogwood blight can have a significant impact on the health and appearance of the tree. Infected trees show leaf spots, wilting, and premature leaf drop, which can lead to defoliation and reduced vigor.

In severe cases, the disease can cause branch dieback and even kill the tree. However, with early detection and proper management, the prognosis for affected trees can be improved.

Least Susceptible Dogwood Varieties

While all flowering dogwoods are susceptible to blight, some varieties show more resistance than others. These include:

• Kousa dogwood (Cornus kousa)
• ‘Stellar Pink’ dogwood
• Other hybrids of Cornus florida and Cornus kousa.

Symptoms and Diagnosis

Recognizing the symptoms of dogwood blight and diagnosing the disease early can help in its effective management.

Early Symptoms

Dogwood blight often begins subtly with small leaf spots as the first noticeable sign.

These spots are usually purple-bordered and may initially appear on the lower leaves before spreading to the rest of the tree. The spots are typically circular and may be surrounded by a faint halo.

In addition to leaf spots, you may also notice a slight curling or wilting of the leaves, even when the tree has been adequately watered.

These early signs can be easy to overlook, so regular inspection of your Dogwood trees, especially during the wet spring months, is crucial for early detection.

Symptoms as Disease Progresses

As dogwood blight progresses, the symptoms become more severe and easier to identify.

The leaf spots grow in size and change in color, turning from purple to tan or brown. The leaves may start to yellow around the spots and eventually fall off the tree prematurely, often while the leaf is still partially green.

This can lead to significant defoliation, leaving the tree with sparse foliage.

In addition to leaf symptoms, dogwood blight can also affect the branches of the tree. Infected branches may show signs of cankers or sunken areas, which are often discolored and may ooze sap.

In severe cases, the disease can lead to the dieback of branches, starting from the tips and moving inward towards the trunk.

Diagnostic Techniques

Diagnosing dogwood blight can be challenging as the symptoms can be similar to other diseases. However, a combination of symptom recognition and laboratory testing can help confirm the diagnosis.

The first step in diagnosis is a thorough examination of the tree. Look for the characteristic leaf spots, wilting, and premature leaf drop. Check the branches for signs of cankers or dieback.

If dogwood blight is suspected, a sample of the infected leaves or branches can be sent to a plant diagnostic laboratory for confirmation.

The lab can isolate the pathogen from the sample and identify it under a microscope. This can provide a definitive diagnosis, allowing for targeted and effective treatment.

Management and Control

Managing dogwood blight involves a combination of cultural practices and chemical control.

Cultural Practices

Remove and destroy infected leaves and branches to reduce the source of infection. Improve air circulation by thinning the branches, and avoid overhead watering to reduce humidity around the tree.

Maintain the tree’s health through proper watering and fertilization to increase its resistance to the disease.

Chemical Control

Fungicides containing chlorothalonil or mancozeb can be applied as a preventive measure during the growing season. Be sure to follow the manufacturer’s instructions for the safe and effective use of these products.

Prevention

Preventing dogwood blight involves maintaining good garden hygiene and promoting the health of the tree.

• Regularly clean up fallen leaves and twigs to reduce the source of infection.
• Plant dogwood trees in sunny locations with good air circulation to discourage the growth of the fungus.
• Water the trees at the base to avoid wetting the leaves.
• Maintain a regular fertilization schedule to promote vigorous growth.

Related Questions:

Why Are My Dogwood’s Leaves Curling?

Leaf curling in dogwoods can be a sign of water stress or a response to certain insect pests or diseases. Overwatering or underwatering can both lead to leaf curl.

Pests like aphids can also cause leaf curling as they suck the sap from the leaves.

If you notice leaf curling along with other symptoms like leaf spots or wilting, it could be a sign of a disease such as dogwood blight.

Why Are My Dogwood’s Leaves Falling Off?

Premature leaf drop in dogwoods can be a sign of stress or disease. Environmental stressors like drought, waterlogging, or temperature extremes can cause leaf drop.

Diseases like dogwood blight or anthracnose can also lead to premature leaf drop.

If you notice leaf drop along with other symptoms like leaf spots or branch dieback, it’s best to consult with a plant disease expert or arborist.

Final Thoughts

Dogwood blight can be a serious threat to the health and beauty of dogwood trees, but with a good understanding of the disease and its management, blight doesn’t necessarily mean tree death.

Routine care and sanitation practices will go a long way in ensuring that your dogwoods continue to thrive and beautify your landscape.

Ready to learn more about common dogwood issues? Don’t miss out on these articles:

• Dogwood Anthracnose: Symptoms, Impacts & Control Methods
• Canker on Dogwood: Causes, Different Types & Management