Oak Leaf Blister vs Oak Wilt Leaf Damage

Each year I try to get my oak trees trimmed in January, before the beetle that can carry oak wilt fungal spores gets active. This is also the time of year when the leaves on my live oaks look the worst. They have been on the tree for almost a year and are beginning to be shed so they can be replaced by new ones. Often I get startled by a few leaves that have browning on them that reminds me of water spotting. This makes me go inside to verify that is not what oak wilt looks like before I get started pruning. This year the browning was much more pervasive than usual so in addition to making sure what oak wilt symptoms look like on live oak leaves, I also wanted to know what the water spotting was and if I needed to do something about it.

It turns out the browning on my live oaks' leaves is oak leaf blister. The images in this post are of leaves infected by the fungus Taphrina caerulescens. Luckily I have not been around oak wilt to get a photo of it for comparison, but you can see what it looks like by clicking here. While oak leaf blister is a major disease of oaks in Texas, it is luckily not a likely death sentence like oak wilt is. After reading about the fungal infection it made sense that I saw much more on my trees this year after after last year's wet spring.

I was glad to know that I did not need to take any further precautions while pruning my trees earlier this year. However in addition to pruning early, I also guard against oak wilt by painting the pruning cuts I make as I work. While using pruning spray has been found to generally be unnecessary, it is an important line of defense for your oaks where there is the potential of infection by oak wilt beetles.