Calendar | Logan County Extension Unit | Ag News Elsewhere [fresh daily from the Web]

Tree talk: emerald ash borer, early falling leaves

By John Fulton

Send a link to a friend

[August 25, 2009]  There have been many findings of the emerald ash borer in central Illinois over the past two years, including Bloomington, Chenoa, LaSalle County and Bureau County. What does this mean for us? It means the borers have been active and undetected in areas for a long period of time. That is part of the problem with the emerald ash borer: It can be in a tree for three to five years before any visual symptoms are available to help us diagnose the problem.

Add into the equation that there are other diseases and boring insects that cause similar problems, and we end up with some confusion. Much of the information Illinois is using has come to us from Michigan State University, where they have been battling the problem for many years. Symptoms of infestation of emerald ash borer include canopy dieback, shoots coming from the base of the tree, splitting bark, serpentine feeding galleries under the bark, increased woodpecker activity and "D"-shaped exit holes. Remember, many other problems cause many of these same symptoms.

The emerald ash borer does not do well moving from one place to another on its own. Most of the help comes from humans moving firewood, lumber or other items made from infested trees. This movement of products is why the insect "leapfrogs" from one place to another, often many miles away.

Many people have asked to have their ash trees looked at to see if they have it. That is all well and good, but remember, it can be in your tree for up to five years before it shows any symptoms that can be seen. The other question is: How do I save my ash tree? To that end, here are some of the things to look at when considering an attempt at insecticidal control.

Phil Nixon, University of Illinois Extension entomologist, lists several things to look at. First, the only certain method to control emerald ash borer is to remove the tree. This sounds extreme, but any control attempt is only effective in the 80-90 percent range. Second, the cost of treatment over a span of years should be looked at. It might cost only $35 to treat for one year, but that will really add up over 20 years, with increasing costs each year. And third, a tree in a regulated area is subject to removal by governmental agencies regardless of whether it has been treated or shows signs of infestation.

There are treatment options for professionals and homeowners to use. It is recommended to preventively treat ash trees no more than 15 miles from known infestations. Control is usually more effective on smaller trees, and treatment is not as effective on trees already infested. The major treatment option for homeowners is to apply Merit (imidacloprid) insecticide as a soil treatment on an annual basis. This treatment will be more effective in the spring, and it takes a month or two to translocate in the tree. Also remember your tree can still be cut down if it is in the zone of a known infestation, whether it has been treated or not.

[to top of second column]


If you see emerald ash borer or its damage, you may call the Extension office at 732-8289 or the Illinois Department of Agriculture at 800-641-3934. More information is available online at and

Falling leaves

With the severe disease and insect pressure we have had, leaves are falling. As we approach September, some of this is to be expected, but some of it is due to damage from insects and diseases. Severely damaged leaves tend to drop early, especially when the leaf attachment is weakened. The causes are various, including bacterial leaf scorch on pin oaks and red oaks, apple scab on apples and crab apples, anthracnose on many good-quality shade trees, verticillium wilt on quality maples and ash trees, and of course Japanese beetle damage on many types of trees.

Bacterial leaf scorch will be an ongoing problem and is life-threatening to trees, as is the verticillium wilt. These diseases plug the tissue that carries water to the plant parts, and there is no control. Fertilization is about the only option (fertilize at the lawn rate to prevent problems to other plants). The other disease and insect problems happen on an annual basis, and trees should leaf out normally next year. You may, or may not, have the problems again next year, depending on the weather.

[By JOHN FULTON, University of Illinois Extension, Logan County]


< Recent articles

Back to top


News | Sports | Business | Rural Review | Teaching & Learning | Home and Family | Tourism | Obituaries

Community | Perspectives | Law & Courts | Leisure Time | Spiritual Life | Health & Fitness | Teen Scene
Calendar | Letters to the Editor