Oak tree leaves turning brown is a common occurrence when it comes to these wooden giants. And we aren’t talking about that nice autumn color, your oak can get under attack by more than a single brown-causing problem.

Oak Tree Leaves Turning Brown

But how to know what exactly bugs your oak, is where we help you; understanding the root cause is the first and main step to dealing with it and saving your oak.

Causes For Oak Tree Leaves Turning Brown

The causes for oak tree leaves turning brown are due to oak wilt, blight, or anthracnose. They could also be due to armillaria root rot that has damaged the plant, or because of bacterial leaf scorch that the leaves are becoming brown. 

Oak trees are famous for their luscious and rounded canopies and beautiful serrated leaves. These are generally considered very resilient tree species and can endure a wide range of winter climates. Oaks will usually be at their weakest when young, which is when you should take special care of them.

– Oak Wilt

This fungal disease attacks almost every oak species and will be the most common cause of those brown oak leaf spots. It’s caused by the Bretziella fagacearum fungus, a dangerous oak killer, and they would start to turn brown.

Oak wilt fungus is surprisingly fast at spreading once it infects your tree, and it does so through water droplets. The disease leads to fast wilting of the leaves and can quickly decimate entire branches, and it would start from the leaves. 

In this case, the foliage would begin to appear bronze and reddish at the outer margins and then progress to the leaf center. You can easily recognize this wilt by scratching the bark too, which will reveal a bluish tissue against the fresh yellow wood coloring.

– Oak Blight

This one is a fungal leaf disease, which causes leaf browning and loss usually in the summer and autumn seasons. Oak blight will typically only attack bur oaks, which are a small acorn variety of oak trees. 

You can generally tell this one by dark brown dots on veins and lower portions of the leaf surface. At the end of summer, just as the fall rains first begin, this disease will expand to larger portions of leaves. Your leaves may turn completely brown and fall off.

The symptoms of leaf blight will often first appear in the lower parts of the canopy before progressing up and outward over the period that you leave this disease unattended. This happens due to the fungal attack which would be caused directly to the roots. 

– Anthracnose

Anthracnose is another fungal disease caused by several types of fungal pathogens. Most of these diseases are specialized in a single tree species, however, with similar effects to the tree and the leaves.

Causes for Oak Tree Leaves Turning Brown

Anthracnose-causing fungi are tree-born species that survive winters in the very tissue of the tree and dormant buds. In spring, this disease is carried a long way by wind and rain and if conditions remain cool and wet they will germinate and cause all kinds of problems.

Anthracnose usually creates brown leaves, making them distorted and curled. If you’re dealing with a severe infection on your leaves, they may soon drop and in quite some numbers. Also note that often causes the most damage in the lower parts of the canopy and young leaves, but may travel up, and harm the whole tree.

– Armillaria Root Rot

Armillaria rot is caused by several fungi from the species of the same name, and this is due to the infestation that would take place below, in the soil, where the roots will be targeted. 

It can survive in the tree tissue for years before its deadly symptoms are triggered. This fungus will occupy the roots and cause wood decay. A healthy tree can slow this process, but weaker ones will succumb faster.

Moreover, this disease will cause reduced growth and browned-up foliage. In some instances, this one can have your tree producing seemingly healthy cones, only to transport them to the next plant in line. 

In short, armillaria is tough to manage and infected trees are on a life sentence of sorts. If you spot some trees that are too easy to break and fall when in storms, they are likely victims of this disease.

– Bacterial Leaf Scorch

When the tree faces leaf scorch, this is one is a systemic tree disease caused by the bacterium known as Xylella fastidiosa. This one infects nutrient-conducting tissues of the trees and is commonly seen affecting a wide range of deciduous species, including oaks.

The first symptom this one shows is a severe browning of leaves in summer, and this one worsens as the season progresses. Sometimes brown splashes are separated from the healthy green tissues by yellow borders, which is how you can identify this disease, and this is exactly how they would spread.

Sick trees usually appear normal and produce a good number of leaves in the spring and the next season, but some branches and leaf sets then suddenly go brown. This one will look just like your normal oak wilt, which is why proper identification is only possible in a laboratory setting.

How To Fix Browning Leaves on Oaks

To fix browning leaves on oaks, you should spray some fungicidal solution, and try to prune out the infested part of the tree. However, if the infested part is big, and you don’t want it to spread, you can burn those parts. 

– Spray Some Fungicidal Solution

Always use a general tree fungicide in spring and summer or a homemade remedy made from neem oil mixed with water. However, you should know that most fungal oak diseases will spread by insects and below ground, and this means that they enter through the roots. That’s why when this happens, one must employ proper control measures.

To prevent insect spreading and control; as a result, you shouldn’t cut or wound healthy oak branches often and especially during summer and spring. These seasons are when the tree enjoys a healthy amount of sap flow but are because of this same reason highly susceptible to transmitting diseases. 

However, you can also ask for professionals to spray chemicals and to get rid of the under-the-ground disease spread should be done towards the roots. In most cases, medicine is applied to the root system, and the system is separated from other trees by a safety line in the ground.

– Prune Out the Infestation

On another note, you should always cut the infected tree parts in the fall, which will give your trees abundant time to heal.

Fix Browning Leaves on Oaks

It’s also a perfect time to cut because the sap will slow down, and the disease spread will be greatly reduced.

– Burn the Infected Parts

Unfortunately, scorch doesn’t have a cure! It can go away on its own but is completely manageable if you implement proper techniques.

Always look to maintain proper tree vigor, not cutting or injuring your tree when it’s in the growing season, essentially in spring and summer.

Practice good sanitation, burn the infected branches you cut off in the fall, and avoid planting susceptible species too close to one another.

Other means of fighting this disease include root flare injections, which can reduce bacteria levels and delay symptoms for a few weeks so that you can enjoy the trees in spring.

Inspect Browning Leaves on Oaks Tree


Oak leaves going brown is no pretty sight, especially when you know some culprits will never go away.

But all of these are completely manageable and even preventable if you apply what we’ve said:

  • Inspect your leaves close up, as some diseases will attack only leaves exclusively, while you need to dig deeper under the skin with others.
  • Some diseases like wilt or blight are completely curable and manageable, while with others like root rot or leaf scorch, you’ll be looking at years of labor to bring your oaks back to health.
  • That’s why prevention is your best bet, and applying pesticides and fungicides throughout the growing season will have the best effect.

Now we know how to handle those browned leaves we can do our best not to have them infected with the above-mentioned diseases!

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