We had a very unusual sample from an oak tree brought into the Extension office this week. On first glance, the problem could have easily been misdiagnosed as broadleaf herbicide damage as the leaves were curled and misshapen. However, close inspection revealed disfigured veins several times their normal size on the back side of the leaves leading to the diagnosis of vein pocket gall. Read More...
The Extension office is being overrun right now with inquiries about problems with oak and sycamore trees. The two issues are completely unrelated so we will discuss them separately.
Anthracnose is a fungal disease that is very common to sycamores. I suspect part of the reason why we are getting a number of calls on it has to do with the drought; it’s been so dry the last few years that the disease has not been as serious as usual.
The good news is the disease is not fatal to sycamores. The bad news is it makes them look bad for much of the season as it often causes premature leaf drop. Since the disease is not fatal to the tree, control measures are not ordinarily suggested. However, if you have a high value tree and want to do everything you possibly can for it, some treatment can help. IF the tree does drop its leaves and puts on a second set, a fungicide labeled for anthracnose can help protect the tree. It will not help to spray now if you are already seeing leaves curl and drop, wait patiently for the new leaves to come out.
We are also receiving many calls on malformed oak tree leaves. In every case so far, this has been related to damage from galls of one form or another. Oak leaf vein gall seems to be especially bad. It is characterized by an odd growth along the vein of the leaf that eventually leads to severe malformation. Galls can also take on many other forms, ranging from resembling fruit to looking like something from a science fiction cartoon. See OSU Fact Sheet #EPP-7168, Galls Formed by Insects and Mites for detailed information and what galls can look like.
Galls are another case where treatment is not warranted. While they can do significant cosmetic damage, they do not hurt the tree long term. That is good, because control of the insects or mites that cause the galls are very difficult.
For more information of this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at firstname.lastname@example.org, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.
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