Tree Care

The Top 5 Tree Diseases and How to Prevent Them


May 9, 2023 


As a member of Strobert Tree Service, our clients often ask us about the importance of preventing tree diseases. Trees are not just a beautiful addition to our landscapes; they play a vital role in our ecosystem by providing oxygen, shelter for wildlife, and even helping to combat climate change. However, like any living organism, trees can be susceptible to diseases threatening their health and survival.


That’s why it’s essential to be aware of the top 5 tree diseases and how to prevent them from affecting your trees. By taking preventive measures and seeking treatment early, you can protect your trees and ensure they thrive for years.


Top 5 Tree Diseases Affecting Trees in the Delaware Region

Trees are essential to the Delaware landscape, providing shade, beauty, and a home for wildlife. However, trees are also susceptible to various diseases, which can damage or even kill them. Here is our list of the top five tree diseases affecting trees in the Delaware region and their symptoms, causes, and treatments.


1. Dutch Elm Disease

Dutch elm disease is devastating and can kill elm trees within a few years. The condition is caused by a fungus that beetles spread. Symptoms of Dutch elm disease include wilting leaves, browning branches, and the tree’s death. There is no cure for Dutch elm disease, but steps can be taken to prevent its spread, such as removing infected trees and keeping beetles away from healthy trees.


2. Ash Borer

Ash borer is an invasive insect that is native to Asia. The insect was first discovered in the United States in 2002 and has since spread to 35 states, including Delaware. Ash borer attacks ash trees, and it can kill a tree within a few years. Symptoms of ash borer infestation include D-shaped holes in the bark, wilting leaves, and the death of branches. There is no cure for ash borer infestation. Still, some steps can be taken to prevent it, such as planting resistant ash trees and inspecting trees for signs of infestation.


3. Oak Wilt

Oak wilt is a fungal disease that can kill oak trees within a few weeks. The condition is spread by beetles, most common in red and pin oaks. Symptoms of oak wilt include wilting leaves, browning branches, and the tree’s death. There is no cure for oak wilt, but steps can be taken to prevent its spread, such as removing infected trees and keeping beetles away from healthy trees.


4. Canker

Canker is a disease that can affect various trees, including maples, oaks, and pines. A fungus or bacteria causes a canker to kill a tree if not treated. Symptoms of canker include dead or dying branches, recessed areas on the bark, and gum formation. There are a variety of treatments for canker, depending on the type of canker and the severity of the infection.


5. Powdery Mildew

Powdery mildew is a fungal disease affecting various trees, including maples, oaks, and pines. Powdery mildew is most common in humid weather, and it can cause unsightly white patches on the leaves of trees. Powdery mildew is not usually fatal to trees. Still, it can weaken them and make them more susceptible to other diseases. There are a variety of treatments for powdery mildew, including fungicides and horticultural oils.


Prevention and Treatment

The best way to protect your trees from disease is to prevent them from getting sick in the first place. There are several things you can do to prevent tree diseases, including:


  • Plant-resistant varieties of trees.
  • Water your trees deeply and regularly.
  • Fertilize your trees according to the directions on the fertilizer label.
  • Prune your trees regularly to remove dead, diseased, or damaged branches.
  • Keep your trees free of debris.
  • Inspect your trees for signs of disease regularly.

If you find that your tree has a disease, treating it as soon as possible is crucial. The sooner you treat a disease, the more likely you will be able to save your tree. Various treatments are available for tree diseases, depending on the type of disease.


If you need help treating a tree disease, it is best to consult a certified arborist. An arborist can diagnose the condition and recommend the best treatment.



Protecting our trees from diseases is crucial for a healthy environment. By being aware of the top 5 tree diseases and taking preventive measures, we can help maintain the health and beauty of our trees. Don’t hesitate to take action – contact Strobert Tree Service in Wilmington today to schedule a free assessment with our ISA-certified arborists with over 20 years of experience. Let’s work together to ensure the longevity of our precious trees.


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