Oak decline is the last of the oak tree diseases we will discuss in our series. The fungus that causes oak decline is Cephalosporium diospyri. It’s a weak vascular pathogen occurring in Texas Trees. Plants affected by oak decline first show signs of thinning out in the top of the tree. When you first notice it, twigs in the upper portion of the tree will show signs of dieback. It will increase yearly if left untreated.
If the dieback reaches the larger limbs, such as the ones in the main tree canopy, sucker growth will become evident on the main scaffold limbs. If the disease is allowed to progress, only the main scaffold limbs will remain alive. Unfortunately, not for long as they will eventually die too. This can take from five to ten years to happen on live oaks, but can happen quicker on other types of oaks.
Therefore, it’s important that – as soon as you notice the dieback on the twigs – to contact a professional like us to help you keep your tree alive. Oak decline is a tree killer and therefore a very serious oak tree disease. We can be reached at 512-341-8888. Although we don’t diagnose tree diseases, we can work with any one of them once they are discovered.
Did you know that root grafting is suspected as one means of spreading the fungus? Root grafting is the process of grafting a shoot or stem of one plant onto a section of another. We don’t suggest you undertake this process yourself. Bark beetles have also been associated with the spread of oak decline. The fungus has been isolated from the body of these insects. If insects are involved, then this would explain the spread of the disease across areas too great for root grafting and can make oak decline more common than was previously thought. It’s not good news, we can assure you.
Live Oak, Post Oak, Water Oak, Texas Red Oak, Willow Oak, Sycamore, persimmon, Winged Elm, Hackberry, American Elm, and Western Soapberry are reported to be hosts for oak decline. There is not a simple method of identifying the disease at this time. For the most part, recommendations are based on positive identification of the problem. Mechanical injury to the roots can cause symptoms easily confused with disease caused by other fungi. In newly built areas, the damage most often observed is from root injury.
Steps to Reduce Live Oak Decline Losses:
- Identify the problem.
- Reduce the stress conditions that weaken trees.
- Optimize fertilizer and water applications to tree.
- Remove dead limbs on tree.
- Do not import wood from Oak Decline infected areas as it could be a source of the disease spread into a previously disease free area.
- Use trees not known to be a host of Oak Decline.
The following trees are known not to be hosts of oak decline:
- Cotton Wood
- Bald cypress
- Arizona Cypress
- Pear (Bradford)
- Osage‐orange Sweetgum
- Crab Apples Mesquite
- Hercules Club
- Redbud Honey locust
- Chinaberry Boxelder
- Palms Mountain
- Chinese Tallow
- Oriental Oaks
- Chinese Holly
When selecting trees, you should contact the County Extension Agent in your county for those trees that do well. You can also contact us at Austin Tree Service. We know which trees work best in our climate.