Oak trees are notable for their size and strength. They’re also one of the most common trees in the St. Louis area and in the Midwest. Oaks are robust trees with generally strong root systems that contribute to their excellent stability, even in the face of violent windstorms.

But even the sturdiest trees and plants can face serious threats. In the case of oak trees, many diseases can attack even the mightiest oak. However, knowing these durable trees face threats and keeping your eyes open can save your oak, and possibly you and your home from harm should one of your oak trees fall prey to disease.

Below are three of the most common diseases oaks face, how you can identify them and what can be done to successfully treat and save your tree:

Armillaria root rot

Armillaria root rot is caused by several species of armillaria fungi. This condition stunts a tree’s (many species of trees can be afflicted by this form of root rot) growth and will, in many cases, lead to the death of the tree.

While the damage is occurring in the roots, trees exhibit above-ground symptoms of armillaria root rot, including:

• Large groups of light-colored mushrooms growing around the tree’s base or on the top of its root flare
• Large patches of black fungal strands growing in a net-like structure on the tree or in the surrounding soil.
• An abnormally large number of acorns (known as a “stress crop” produced by the afflicted tree
• Death of foliage in the upper part of the tree, or smaller or miscolored leaves

Treatment for root rot can vary according to a tree’s circumstances and can include mulching around the tree’s base, removal of any nearby rotting and infected stumps, and limiting foot and other traffic, which can compact the soil around the tree.

Oak leaf blister

Caused by taphrena caerulescens fungus, oak leaf blister is rarely fatal. However, over time it can stress and weaken trees, making them more susceptible to other diseases, infections, and storm damage.

Oak trees suffering from oak leaf blister show noticeable symptoms. These include yellow-white circular raised areas on the upper surfaces of leaves and brownish-yellow matching depressions on the lower surfaces of leaves. Trees with severe cases of oak leaf blister will often drop their leaves in early summer and may also grow new leaves weeks later.

Once properly identified, oak life blister can be treated with fungicide spraying using chlorothalonil applied after buds appear and before buds break. Early identification and proper timing of treatment are key to treating oak leaf blisters.

Oak wilt

Oak wilt is an aggressive, contagious oak tree disease caused by Ceratocystis fagacearum. The disease – which is often lethal – is usually spread through the root systems of trees or by wood-boring oak beetles.

In red oaks, oak wilt causes noticeable symptoms, including dead branches beginning at the top of the tree, leaves turning pale green or bronze around their edges, drooping or wilting leaves, often rolling lengthwise, and dropping leaves. White oaks also exhibit similar symptoms, though they typically resist oak wilt better than do red oaks. However, the disease is life-threatening to white oaks, though it will generally progress more slowly than in red oaks.

Unfortunately, there is no cure for oak wilt. Still, identification is extremely important as afflicted trees should be cut down, and their root systems removed to prevent the spread of the condition to other trees. It’s common for large stands of oaks to be destroyed by oak wilt if it is not identified.

Identification is key

Tree diseases caused by fungi, bacteria, or insects can be difficult to diagnose. Saving trees or groups of trees, however, depends on proper identification of the condition and timely treatment. While some conditions can be treated by homeowners, a misdiagnosed condition and the incorrect treatment can worsen the situation.

If you see any of the symptoms described above in one of your oak trees, contact Hansen’s Tree Service. Our certified arborists will correctly diagnose and explain your tree’s condition and prescribe an effective course of treatment. We’ll also carry out any necessary treatment, ranging from spraying or pruning, to complete removal of an afflicted tree and its root system. Contact us today!