Current Issue Affecting North Central Texas Oaks: Tubakia Dryina Leaf Spot
Published August 13, 2020 By GREG CHURCH, Ph.D.
We have visited several properties recently with concerned tree owners because of the deterioration of leaves on their Oak trees. Primarily, what we are finding are symptoms of Tubakia dryina leaf spot (formerly known as Actinopelte). Many types of Oaks can develop this late-season leaf disease; however, it is more prevalent in the Red Oak group (such as the Black, Red, and Pin Oak).
The symptoms to look for in an infected tree are leaf spots between 1/4 to 1/2 inch in diameter that are dark to reddish-brown. The spot is often accompanied by an outer circular lighter or yellowing ring. Leaves that are severely infected will prematurely defoliate.
Though this type of fungal tissue affects the appearance of the tree, it usually develops late enough in the season that there are no long-term adverse effects on tree health. As a result, treatment with fungicides is usually not recommended.
However, you may want to look for other issues that could be causing the infected tree stress. If possible, improve the tree’s conditions or environment (ie. mulch, fertilization, watering deeply, etc.) since stress makes a tree more susceptible to pathogens, such as Tubakia dryina.
To limit re-infection, it is advisable to rake all of the leaves when they fall this autumn and dispose of them in the garbage. It is also best not to have your yard service mulch the leaves while mowing. The spores on the leaves should be cleared entirely from the yard.
Plant diseases that infect the leaves of trees are more common when we have frequent rainfall in the spring. The longer the leaves stay wet after rainfall increases the chance the leaves can become infected with a disease. Proper pruning of your trees can help improve the airflow through the canopy and reduce the amount of time that the leaves stay wet after rainfall. Contact our office to schedule an inspection of your trees for disease and pruning recommendations.