The Plant Disease Clinic has received reports of oak trees with deformed leaves in Scott County and Iowa County. The oak leaves look as if they have been eaten away by insects, with the tissue between the veins almost entirely missing, giving the leaves a lacy or tattered appearance. From a distance the trees may appear to lack leaves or be pale in color. Symptoms appear when leaves begin to emerge on the trees, generally middle to late May. White oaks are the most commonly reported with these symptoms, although the damage also has been seen on members of the red oak group, hackberry, and other tree species.
Oak tatters is the name commonly given to this disorder. The cause of oak tatters is unknown, although it apparently results from damage to the developing leaf tissue while in the buds or as the buds open. This damage is probably caused by cold temperature injury, although insect feeding or egg-laying and herbicides also may be involved. However, none of these has been proven.
Trees with oak tatters typically produce a new flush of leaves to replace the tattered ones. The extra energy required to produce these extra leaves may deplete the energy reserves of the tree, making it more susceptible to other disease and insect problems. Because of this, trees with oak tatters should be kept as unstressed as possible. Trees should be protected if site changes are planned. Newly established trees can be mulched to reduce competition with grass. Finally, trees should be adequately fertilized and watered (primarily during extended dry periods) to maintain tree vigor.
A bulletin with pictures and a description of oak tatters is available from the US Forest Service.
This article originally appeared in the 5/28/2004 issue.