It’s that time of year again, the leaves are green, the flowers are blooming, the birds are singing, the oak leaves are blistering. Ah spring! Wait a minute- oak leaves blistering? Yes, this is a common sight this time of year. Oak leaf blister is a common leaf disease on oaks in Florida. It can affect any oak but it seems more prevalent on laurel oak. This disease is more prominent after a cool wet weather, so we can expect to see a lot of oak leaf blister this spring. The spores of this fungus infect newer leaves and cause swollen blister-like tissue like you see in this photo (courtesy Okeechobee County Extension):
Oak leaf blister can also cause leaf distortion and leaf curl. In most cases this is just a cosmetic problem and rarely does any significant damage to an oak. This fungus only attacks the leaves and will not cause harm to the rest of the tree. In some extreme cases on a younger tree you may experience a large leaf loss. If that is the case you should rake up the fallen infected leaves and dispose of them to avoid spreading the fungal spores to your other trees. Otherwise, enjoy the shade of your oak and get some gardening done before it gets too hot!