By: Bobby Smith

I have had several calls the last two weeks dealing with homeowners’ oak trees. Upon inspection of the leaves of the trees, I find they have blisters that start as light colored round spots on the upper side of the leaves and the lower surface has grey depressions that correspond to the blisters. As the disease progresses these blisters turn brown and have that semi-round shape and water soaked appearance and the leaves will curl as the blisters coalesce. Premature leaf drop may also occur.

Oak leaf blister caused by the fungus Taphrina caerulescens is a common disease affecting many species of oaks. Members of the red oak group are particularly susceptible to infection but all oak species are susceptible and I have seen it in water oaks as well. Disease development is favored by cool, wet springs like we have had this year. In years when such conditions occur, noticeable leaf deformity results. Heavy infections of oaks impair their appearance but do not endanger the tree health. Leaves become infected when buds are beginning to open in the spring. The pathogen can survive winter on plant twigs and bud scales. Spores causing oak leaf blister are spread by wind and rain.

The control of this disease is simple. Rake fallen leaves and debris and discard to reduce disease inoculum. No chemical control is necessary. If you have questions about your tress contact your local UGA Cooperative Extension office at 1800ASKUGA1 or 18002758421.

Printed in the June 18, 2009 Edition.