August Tree Update

Home Grown  by Keith Reed
An increasing number of calls are coming into the Payne County Extension office about the condition of our area trees. Specifically, clients are seeing lots of browning and early leaf drop. While we can’t say for certain what might be causing a problem with a specific tree, here’s a general summary of what we are seeing and what, if anything, you need to do about it.

• Our early season weather seems to be the biggest contributor to the symptoms we are seeing now. Think back a few months: We had a very early green-up with tender leaves opening up earlier than normal. Then we transitioned into a long, cool, damp period. This was the perfect formula for leaf spot fungal diseases to move in on a variety of plants, not just trees.

A close inspection of leaves early in the season could have identified the disease-causing culprit, not that correct ID is of critical importance since treatment is only rarely suggested anyway. However, by this time of year, most of the diseases have run their course and the only thing that remains is a browning, tattered leaf. This makes is more difficult to determine the exact cause of the problem. The good news is this should not cause any long term harm to an otherwise healthy tree.

• Dutch Elm Disease (DED) continues to take out a few elms every year and this year will probably be no exception. However, just because an elm is turning brown does not automatically mean DED is the cause. The leaf spot diseases mentioned above plus the presence of leaf-chewing insects can also cause the decline. If your tree leaves are gradually declining all over the plant, it is nothing to be concerned about.

Of greater concern would be when one or two branches turn completely brown in a short period of time, with the adjacent branches taking on a wilted appearance. DED kills trees by clogging the vascular system. If you envision the water supply be choked off to increasingly large parts of the plant, you can better understand the symptoms.

If you see signs of possible DED, always look carefully at the condition of the branches before jumping to conclusions. Elms are weak wooded trees and are easy damaged with broken or twisted limbs all too common.

• While we have been spared from this for the most part this season, storm damage from high winds are a common contributor to browning of small groups of leaves. Similar damage also happens occasionally from twig girdler insects. Once again, this is nothing to worry about for the long-term health of the tree.

Construction damage also tends to show up this time of year as the stress of summer settles in. Examples are almost everywhere. If we see a mature tree in sudden decline, the first thing we look for is recent disturbance near the root zone. Sadly, this is an issue that can only be prevented; there is no “cure” once the damage is done. If you have important trees in your landscape, talk to a professional arborist or contact us well before you begin construction.

Keith Reed is the Horticulture Educator in the Payne County Extension OSU Extension office. You can contact him via email at keith.reed@okstate.edu, call 405-747-8320, or stop by the Payne County Extension Office at 315 W. 6th in Stillwater.

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