What’s Happening to My Live Oak Trees?

This spring (2020) has seen almost every Live Oak in Denton County infected with a disease call Oak Anthracnose. This sound like a terrible disease, but it is really just a nuisance for the trees. This is a fungal disease and affects the leaves only on Live Oaks. The infected leaves turn brown and curl on the edges and eventually drop from the tree. The tree will replace the lost leaves and normally, by mid-summer, the tree crown is full again. If your tree has leaves that look like those in the photo below, it is most likely Oak Anthracnose.

Anthracnose is a general term, or family of diseases that affects trees of different species in similar ways. Each tree species Anthracnose is caused by a specific fungus unique to the species of tree. There is Elm Anthracnose, Oak Anthracnose, Ash Anthracnose, etc., but they all exhibit very similar symptoms on the tree. Only in a few (such as Ash Anthracnose) can the disease cause long term damage to the tree. Anthracnose, in general, is characterized by leaf spots, cupping and curling of leaves, and early leaf drop.

The disease is common when the spring weather is cool and wet. If the environmental conditions are just right (temperature, humidity, and the presence of fungal spores) then the disease occurs. We have seen a lot of this on Lacebark Elms this spring also. The disease on Elms is also called Elm Black Spot.

Control is rarely recommended. Once the disease has manifested itself, it is too late to treat. In some instances, when the disease is chronic in a tree year after year, treatment may be warranted, but it is not common.

Let the disease run its course in your Live Oaks. It is recommended to rake up the infected leaves and dispose of them to remove the next year’s inoculum from your property.

If you would like a full evaluation of your trees, please contact our office at 972-317-9598 to have one of our ISA Certified Arborists visit your property and provide an in-depth assessment and diagnosis. Oak Anthracnose, and other diseases, may indicate more primary factors that are affecting the tree’s health and vigor.