Oak Wilt - The Silent, But Deadly Killer of Oak Species

Have you ever heard of Oak Wilt? If you have, you know about the severe threat it poses to Oak trees. If you haven't, no worries! This blog provides insight into what oak wilt is, what causes it, symptoms to look out for, and management tips on effectively controlling this nasty fungus from causing complete failure of your trees.

What is Oak Wilt?

Oak wilt is a lethal disease caused by the fungus Bretziella fagacearum and attacks species of red and black oak trees. The oak wilt fungus can spread from tree to tree via root grafts or above the soil via pests. The Black Oak, Blackjack Oak, and all Red Oak species are the most susceptible oak species to this oak wilt and can die very quickly (some within a matter of weeks).

How symptoms of Oak Wilt vary in different Oak species:

Oak trees boast a whopping variation of nearly 17 different species. These species are often classified into two separate groups: either red and black oak or white and bur oak groups. Symptoms usually present differently depending on the species of oak affected by the fungus. Below are some details on how the symptoms of oak wilt manifest differently between the two groups.

Red and Black Oak Group

Oak trees in the black and red group are far more susceptible to oak wilt than the white or bur oak groups. Red and black oaks tend to become infected by oak wilt disease near the beginning of the summer season.

The first symptoms that present themselves at the onset of an oak wilt infection occur in the uppermost portions of trees. Leaves on infected red and black oak trees will begin to turn a dull tan hue, starting at the leaves' tips and edges and continues to progress down to the base of the leaf. However, the base of the leaf tends to maintain its green hue, and the division between the tan and green tissue on the leaf is often an abrupt one.

It's essential to monitor your trees for these symptoms when the infection infiltrates the tree, as the infection often spreads rapidly throughout the tree, resulting in quick wilt and the ultimate death of the tree by the end of the season.

White and Bur Oaks

The white and bur oak group of species tend to be far more resistant to oak wilt disease than the rad and black group. Symptoms in white and bur species present themselves at a more gradual rate. This usually includes only one limb or a handful of limbs scattered throughout the tree that become infected and present symptoms. The disease will begin to work its way down the tree and usually only makes it a short distance within one growing season. Some species can begin to experience premature leaf drop; however, it's usually not as pronounced. While infected white and bur oak trees are resilient and can endure the side effects for several years before death, the infection will cause limbs to dies throughout the crown, becoming progressively noticeable each year as the disease spreads throughout the tree over time.

Preventative Methods

While there is no cure for oak wilt, there are preventative methods established that can help to prevent the infection from continuing to infiltrate other areas of the tree to protect your oak trees. Below are some of the recommended methods of prevention:

Wound prevention and treatment:

Act fast when you discover wounds from oak wilt on your trees. These wounds invite pests that can carry the fungus and accelerate the spread throughout the tree.

Sanitary pruning:

Sanitary pruning is the practice of removing infected branches from the tree's crown using proper pruning cuts. This method is often used in more resilient white and bur species.

Disrupt root grafts:

The source of transmission of oak wilt often occurs in the root system on the tree. Oak trees planted in close proximity to other oaks can begin to fuse their root systems, forming root grafts creating a direct path for the fungus to spread to the other tree and infect. It's crucial to hire a professional arborist to execute this method safely and effectively.

Apply preventative fungicides:

For this method, a professional arborist uses an applicator to inject all oak species with a fungicide to protect healthy trees from a potential infection. This method can be used in infected oak trees; however, it cannot cure the infection and is merely a preventative measure.

No matter the species of oak you may have, you must be proactive in treating it at the first sign of any symptoms. It's also best to work with a professional arborist trained in oak wilt prevention methods to ensure proper treatment of the tree. Please don't hesitate to call our team if you have oak trees on your property. Our teams of arborists come expertly trained to identify and help you protect your trees from the devastating effects of oak wilt.