What Is Killing My Oak Trees?

Monitor your oak for new growth to judge if it is regaining its health from a fungal disease.

Oak trees can die from a variety of environmental factors, such as fungal diseases, severe drought and pests. Gardeners should monitor their trees for signs of declining health. It is imperative for the health of your oak to determine what is causing its death. Treatment may be available, depending on the cause of the ailment.

Diseases

Oak trees can suffer from diseases such as oak leaf blisters, anthracnose, rust, powdery mildew and actinopelte leafspot. Signs that your oak tree has contracted a disease include leaf distortion, foliage discoloration, defoliation, twig dieback and leaf spotting. Typically, gardeners can treat their oak trees with fungicide. Pruning out diseased branches and watering your oak trees can help them fight the disease. Furthermore, fertilizing the tree will provide extra nutrients to promote healthy growth.

Drought and Over-Watering

Drought can be the last straw for oak trees that are already declining in health. Thirsty root systems add stress to already diseased oak trees. Over-watering or excessive rainfall compact the soil. Compacted soil holds less oxygen, which causes a buildup of carbon dioxide and other toxic chemicals. Giving your oak trees supplemental water during dry spells will keep your tree from succumbing to disease.

Damage

Oak trees have deep taproots underneath them, but they also grow long shallow roots. In fact, mature oak trees can grow shallow roots 90 feet away from the trunk of the tree. These long roots pose a problem for gardeners trying to mow the area. You can damage the long surface roots with your lawn mower's blades. Wounds made in the roots create pathways for diseases and harmful pathogens to enter. It is important to examine how far your oak's root system extends and to avoid mowing that area.

Pests

Oak wilt is a serious disease that effects the thousands of trees in the northeastern United States. This disease is spread by insects such as nitidulid beetles. When oak trees have been damaged, they release a sap that attracts nitidulidae, also known as sap beetles, carrying the oak wilt disease. They visit the oak tree and transmit oak wilt's fungal spores. Your infected oak tree may exhibit leaf discoloration, defoliation and streaking wood. Any oak-wilt-diseased oak tree should be removed from the yard and thrown away or burned.

References

• Neighborhood Association of Southwestern Williamson County: Oak Tree Diseases
• Florida Department of Agriculture and Consumer Services: Common Causes of Oak Mortality; E.L Bernard
• California Oak Organization: Oak Tree Care
• Northeastern Area State and Private Forestry Services: How to Identify, Prevent and Control Oak Wilt; Jennifer Juzwick