These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area.
May Trees Look Ragged
June 1, 2000
Leaves on many trees look a little ragged this season. Some trees get leaf diseases that may be the cause, but many problems this season are due to the weather. In most situations, the actual damage to tree health is not as serious as it looks.
Spring weather has caused a variety of problems. Much of northern Illinois has had storms with high winds and hail in May. In addition, unusual warmth in early March was followed by some very cold weather in March and late frosts in April and May. All of these factors have added up to damage to newly emerging leaves on trees.
Typical injury will appear as ragged foliage, in particular on maples and other trees with large leaves. There may be holes in the leaf interior, frequently appearing in a symmetrical pattern, as the damage occurred as the leaf developed in the bud. Injured leaves also may have torn or ragged edges. Often this type of damage is confused with insect feeding. Frost injury may also cause blackened areas on leaves.
Oak leaf skeletonizing, or oak tatters, has also been common this season.
Much of the leaf is gone, leaving veins and maybe some callus tissue.
White oaks are most prone to this disorder. Apparently this condition
is due to cold injury to leaves when they are still in the bud. The extent
of tree damage to these weather related problems largely depends on what
stage of development the particular tree was at when the winds, hail,
or frost hit. Not much can
In addition to weather damage, leaf diseases can also be seen on many trees. One of the more common is anthracnose, a fungal disease that is favored by cool, wet weather as leaves are developing. Anthracnose will appear as blotches or irregular patches on leaves, usually brown or tan in color. Ash, maple, and oak are among the trees this disease may appear on. At this point, not much can be done, but the leaf disease is not considered a threat to overall tree health.
With all these types of problems, the best advice is to avoid any additional stress to the trees this season. Most of northern Illinois has had adequate rain recently, but if the summer turns dry, water affected trees to minimize stress. As always, avoid damaging trunks and root systems when working near trees this season.