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A Comprehensive Guide to Identifying and Treating Diseases in Trees

Trees are an integral part of the natural environment, providing vital resources such as oxygen, shade, and habitat for animals. Unfortunately, trees are also vulnerable to a variety of diseases and pests that can cause significant damage or even death if left untreated. This guide is designed to help you identify and treat diseases in trees so that you can maintain the health and beauty of your trees for years to come. With detailed information about common tree diseases and their treatments, you can keep your trees healthy and safe. So let’s get started on your journey to becoming an expert disease diagnostician and tree caretaker!

Identifying Tree Diseases

There are many ways to identify tree diseases. Some of the most common are visual identification, tree health evaluations, and laboratory tests.

Visual Identification

The easiest and most common way to identify tree diseases is visually. When a tree has a particular disease, the leaves, shoots, and branches will be discolored, wilted, or distorted in some way, making it obvious that the tree is infected.

Tree Health Evaluations

Another helpful way to identify tree diseases is through a tree health evaluation. This involves looking at the overall health of the tree, such as its size, shape, and condition of its leaves and branches.

Laboratory Tests

A third way to identify tree diseases is through laboratory tests. If you suspect that your tree may have a specific disease, you can send a sample of its tissue to a laboratory for testing. This is especially helpful for diseases that are too rare or difficult to identify with a visual inspection.

Common Tree Diseases

When trees become sick, the symptoms vary depending on the type of disease. Diseased trees may display any or all of the following symptoms:

Wilting and Drooping of Leaves or Branches

This is one of the most common signs of tree diseases. This happens because trees use water to transport nutrients and sugars throughout their bodies. When trees are sick, they tend to use extra water to fight off diseases, which can lead to wilting and dying branches.

Change in Color of Leaves

A tree’s leaves are a sign of its overall health. When trees are sick, their leaves may become discolored. Leaf discoloration can be caused by a variety of diseases, so make sure to inspect the rest of the tree for other symptoms.

Treating Tree Diseases

Trees are extremely sensitive to disease, and many common tree diseases are difficult to treat. However, there are several ways you can treat tree diseases. These methods include biological control, chemical control, and cultural control.

Biological Control

This is a method of reducing tree diseases through the use of beneficial insects, fungi, and bacteria. Biological control is often used in organic tree care, and it can be an effective way to treat tree diseases.

Chemical Control

This is any method that uses artificial chemicals to kill tree diseases. Chemical treatments can be effective in treating tree diseases, but they can be harmful to the surrounding environment. 

Cultural Control

This involves altering the tree care method to reduce the chance of disease. Cultural control helps you prevent diseases before they start by maintaining high soil and air quality, avoiding drought, and reducing stress on the tree.

Preventing Tree Diseases

The best way to prevent tree diseases is through proper tree care. By caring for your trees, you can reduce the risk of diseases occurring and having to treat them. You can start by choosing the right tree for your environment. If you are planting a new tree, make sure that it is native to your area, so that it can thrive with minimal care. Additionally, you can reduce the risk of tree diseases by maintaining healthy soil, proper watering, and proper fertilization. Proper maintenance of these factors can help increase your tree’s health, helping it fight off diseases before they start. Finally, make sure that your trees are properly trimmed and pruned. This can help increase airflow around the tree, reduce stress, and make it easier to maintain your tree’s health.

Tips for Maintaining Tree Health

Finally, there are several tips you can follow to maintain the health of your trees. These include:

  • Follow a regular schedule for pruning, watering, and fertilizing – These are some of the most important aspects of healthy tree care, and they can help prevent diseases from taking hold in your trees.
  • Routinely inspect your trees for pests and diseases – You can regularly inspect your trees for pests and diseases. This can help you catch diseases early when they are easiest and cheapest to treat.
  • Choose the right tree for your environment – As mentioned above, trees are most healthy when they are native to your area. Make sure to choose a tree that is common to your area and can thrive in your environment.

Resources for Further Information

Finally, there are many excellent sources of information on tree diseases. If you are interested in learning more about tree diseases, diseases in general, or tree care in general, these articles are excellent resources. Consider reading The Ultimate Guide to Plant Diseases: Identifying and Treating Plant Diseases in Your Garden by Sarah Dykstra or The Tree Doctor’s Field Guide to North American Trees: Diseases, Disorders, and Injuries by Eric Sideman. You can also contact a local arborist in Portland, or wherever you live, for more info on tree disease. 


Trees are a vital part of the natural environment, but they are also vulnerable to a variety of diseases and pests. With this guide, you should be better equipped to identify diseases in trees so that you can maintain the health and beauty of the trees around your home.