A relatively new condition affecting emerging oak leaves, called oak tatters, is again appearing in Iowa.
The condition affects primarily white oaks, including white, bur and swamp white. Red oaks are only occasionally affected.
Damage appears when leaves emerge in mid to late May. The leaves will appear lacy or tattered. Heavily affected trees will produce new leaves that may not have tatters but may be smaller and lighter in color than normal leaves.
Producing replacement leaves reduces important energy reserves. Healthy trees can survive this stress but repeated damage or damages combined with other stress, like drought, other defoliation or site problems, may make the tree more susceptible to decline or to other problems.
“Trees should recover unless they are tattered for three or more years in a row,” said Tivon Feeley, forest health program leader for the Iowa Department of Natural Resources.
The condition appears to be caused by damage to leaf tissue in the buds or as the buds begin to open for leaf expansion. The source of the damage could be from low temperature injury before or during leaf expansion, insects feeding on the buds or developing leaves, or by herbicides affecting the physiology of the tree resulting in abnormal development of the leaves.
In addition to Iowa, oak tatters has been observed in Minnesota, Michigan, Wisconsin, Illinois, Indiana, Ohio and Missouri.
In woodlands, little can be done to prevent additional damage after an oak tatters event, except to reduce other stresses such as grazing of livestock.
For yard or urban landscape trees, try to minimize other stresses like changes to the site, add mulch to the tree and water during extended dry periods.
For more information contact Tivon Feeley, Forest Health Program Leader, Iowa Department of Natural Resources Forestry Bureau, 515-281-4915.