Ash tree dropping leaves this spring, but no need to be alarmed
MADISON – People throughout central and southern part of Wisconsin have been reporting that ash trees have been dropping their leaves since shortly after the trees leafed out, but state forestry health officials say the leaf drop is not likely to cause any long term health problems for trees and affected trees should recover.
“Ash leaf drop was first noticed in many areas of Wisconsin following the Memorial Day weekend,” says Kyoko Scanlon, a forest pathologist with the state Department of Natural Resources. “Due to loss of leaves, affected trees have a thinner crown compared to nearby broadleaf trees of different species, as if they never quite leafed out.”
Scanlon says several events this spring have caused ash to drop some of their leaves and appear thin and sparse. The cool spring temperatures caused ash to leaf out a bit later than usual. Several mid-May freezes as well as patchy frost around the state damaged newly expanding leaves or caused tender leaves to die. In addition, anthracnose, a fungal leaf disease, was able to infect some leaves this spring and the trees are purging those damaged leaves.
“When you look at ash leaves that prematurely fell to the ground, they have black blotches on green leaves and many of them are curled up or distorted,” says Scanlon.
The leaf disease, anthracnose, is commonly seen when the spring weather is cool and wet. Leaf damage tends to be more severe on the lower crown of a tree if anthracnose is the culprit whereas frost damage will be more severe in the upper portions of the tree and the outer edges.
Early leaf drop of ash was also severe and widespread in 2004 when a cool wet spring allowed anthracnose to thrive, according to Linda Williams, a DNR Forest Health Specialist. During that year some ash trees were almost completely leafless in early June, and many homeowners were concerned that their trees would die.
“Those trees started to produce additional leaves, and the affected trees looked much better the rest of the season. The trees didn’t see any long-term ill effect,” she says. “We expect that the current ash leaf drop problem won’t cause any long term health problems and affected trees should recover and have fuller crowns by producing a second set of leaves.”
Once leaves mature, temperatures increase, and spring shower season ends, the problem usually subsides. No control is necessary for yard trees although it is a good idea to maintain the overall health of the trees by watering during dry periods, properly mulching, and minimizing injuries to the tree.
FOR MORE INFORMATION CONTACT: Kyoko Scanlon, DNR Forest Pathologist, Fitchburg, (608) 275-3275 or Linda Williams, DNR NER Forest Health Specialist, Green Bay, (920) 662-5172
