Oak Tree Problems

Oak trees are generally resilient.

Birds and other animals keep the ecosystem on an oak tree in balance. Anna Storsul/Unsplash

Q: The leaves on my newly planted oak tree have numerous holes, and the edges of the leaves are missing. I do not see any insects, but I am worried about the tree. Most of the tree is like this.

A: Oaks are pretty tolerant of many insect pests. Holes in the leaf can be caused by insects or by diseases such as anthracnose that kill areas of the leaf, which eventually fall out, leaving the holes.

Next year, you should watch the leaves starting in the spring. If there are caterpillars or beetles eating the leaves, they can be dealt with then. Spraying the tree now, when there is nothing there to treat, is a waste of money and pollutes the environment.

Oak leaves can have leaf miners that burrow around inside the leaf. They make the surface of the leaf look like a blister before the area turns brown and dies. You can see the insect inside the leaf if you hold it up to the sunlight and look through the leaf.

Diseases will cause spots on the leaf to discolor before they turn brown. Often, large sections of a leaf will turn brown, which is not the case with the insects.

Most likely, you will not have to do any treatments. Oak trees are the backbone tree species in the ecosystem of anywhere they grow. They support a vast array of insects, birds, mammals, and other animals. They tend to shrug off the damage that insects cause to the leaves. Those insects are also part of the ecosystem, and they feed birds. Unless the tree is very small and has a lot of insect damage that threatens its survival, you will probably not need to do anything.

Q: Do you have any information on the reason the white oaks in Lemont are turning light green and then a yellow-green and then dying? There are at least three in the area, two on my property, and one across the street that are suffering from whatever it is that causes this.

A: From your brief description, there are several possibilities. When several trees in a general area all exhibit the same symptoms, it often comes from an environmental problem. It could be something simple, such as too much water from the rains you have been having, that damaged the roots. There’s also the possibility of lightning; we normally think of lightning as something that blows up trees, but it can be spread out and just slightly damage a group of trees that then slowly die.

On the other hand, when several trees get the same thing, it could be a serious outbreak of a disease or insect problem. In this case, oak wilt is a serious and deadly disease that needs to be looked into. The symptoms you list are not specific enough for me to give you a specific answer. Because the trees appear to be dying, not just turning colors, you need to call your local licensed arborist to get an on-site visit.

Another place you can take a few leaves and some pictures to is your local extension office from your state university. There are offices in nearly every county in the United States. They often have master gardeners or horticulturists on staff that can help you.

Courtesy of Jeff Rugg

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