Bur Oak yellow and brown leaves

Question: HiI have 2 bur oaks in my frontyard and both have leaves turning yellow and eventually brown.Trying to understand if it is stress related or some fungal infection.

responder: An Ask Extension Expert Replied August 24, 2024, 3:14 PM EDT
response: Ashish—Please tell me where your tree is located—what part of which county are you in?  The data with your message says Williamson Co, but I  want to confirm.  I ask because soil types can make a difference to bur oaks.  I'm forwarding your photos to AgriLife's  forest service for assistance. Rick Coke

responder: The Question Asker Replied August 26, 2024, 10:12 AM EDT
response: The tree is located in Williamson County in Austin, TX. I am near the South part of county near to Austin city and Round Rock city boundary.

responder: An Ask Extension Expert Replied August 28, 2024, 3:50 PM EDT
response: Ashish,  I contacted the extension service, and received a reply from one of their arborists.  They offered three possible causes: 1)  The trees are affected by anthracnose which will cause leaf drop but usually doesn't kill the tree.  Pick up and trash fallen leaves to minimize the amount of pathogen in the area and top dress out to the dripline with compost. 2)  The trees need water.  Use a soaker around the tree or let the hose run in several places around the tree to thoroughly wet the soil to several inches deep. 3)  Soil and  mulch are too deep around the tree.  Expose the root flare to allow the area to breathe and resist fungal infections. If the trees are in their first year or two in this location, specifically water the root ball in addition to watering the surrounding soil.  The root ball is probably an airy mix with a lot of peat in it and it can dry out more quickly than the soil.  I hope this helps.  I've pasted the arborist's comments below.  Rick Coke   Thanks for sending the photos of the tree. I agree with Kimberlee this is does look like anthracnose foliar pathogen that is commonly associated with abundant rainfall, but I also question how long the tree has been planted and if there has been any supplemental irrigation as temps have increased this month. Depending on when and how the tree was planted it may still be establishing roots and could benefit from supplemental watering. When did the landowner first notice the tree’s canopy change? When was the tree planted?  Is the root flare exposed on the base of the tree or does the homeowner need to excavate to see the buttress roots of the tree ? (see photo below).   You can see in the photo above that the trunk had been somewhat buried by soil or mulch that could inhibit tree health. If the buttress roots are not visible, they should be carefully excavated with hand tools and a broom to allow this area to be exposed to air. If this area has not received rainfall in some time, I recommend the homeowner purchase a drip hose and give the tree a good soak for several hours in the evening (3-4 hours or until the soil around the dripline of the tree is good and saturated). If this area has received decent rain recently (1-2 inches) this may not be necessary, but monitoring would be encouraged. A sample could be sent to the A&M Plant Pathology Lab (see attachment) to determine what foliar pathogen this may be but in general foliar pathogens are an annoyance but not aggressive condition to trees and they will typically drop leaves, put on fresh growth when conditions allow, and if the dropped leaves are not collected and discarded the new leaves can be reinfected as the pathogen’s lifecycle continues. I recommend observing this tree following a deep watering session and if root flare excavation is necessary, allowing for some mulch to be distributed along the tree’s drip line (extent of the tree’s branches) but not directly against the trunk which needs to have airflow for the tree to avoid root rot. If the tree begins to drop leaves collect and remove them with a rake into a trash bag to be discarded. Top dressing with compost may benefit the tree if major leaf loss occurs.

responder: An Ask Extension Expert Replied August 28, 2024, 10:30 PM EDT
response: Ashish— I suggest you repeat your question to the Central Texas Master Gardeners at <personal data hidden>. I'm in Dallas County and our environment is very different than yours.  I don't mind at all trying to help you, but someone who deals with the same plants in similar soils might give you a smarter answer. Rick

responder: The Question Asker Replied August 29, 2024, 9:54 AM EDT
response: THanks Rick for all the info.
I will post to Central Texas Master Gardeners email id provided

Regards
Ashish

On Wed, Aug 28, 2024 at 9:30 PM Ask Extension <ask> wrote:
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