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Tree Leaf
Tree Leaf  

Tree
Tree  
Hello.  I have a tree, which I believe is some sort of ash, that has recently developed some strange brown spots on almost all of its leaves.  The tree is somewhere around 8 years old and has been doing fine up until this year.  We had a very wet and rainy spring and the tree really grew!  I would estimate at least a foot of growth.  It looked fine and was getting very bushy.  I decided I would do some pruning to start shaping the tree.  I removed some smaller branches along the bottom and from a few other spots.  I was gone for a few weeks and during that time there was a normal amount of rainfall.  When I got back and inspected the tree, I found almost every leaf had some strange brown all along the edges.  It almost looks like the leaves were burnt around the edges because there is a black border around where the brown spots are.  Do you have any thought about what might be happening to this tree?  Did I damage it when I pruned it, or is it suffering some sort of disease or bug?  Also, do you think this is an ash tree?  I really appreciate your help and information.  I have tried to attach some images of the tree and of some leaves.  Thanks, Kevin

Answer
No it did not come from the pruning. These are leaf spots--a fungi. Leaf spot is a common descriptive term applied to a number of diseases affecting the foliage of ornamentals and shade trees. The majority of the leaf spots are caused by a variety of fungal pathogens but some are caused by bacteria.

The primary symptom of a leaf spot disease is spots on foliage. The spots will vary in size and color depending on the plant affected the specific organism involved, and the stage of development. Spots are most often brownish, but may be tan or black. Concentric rings or a dark margin around the spot may be present. Fungal bodies may appear as black dots in the center of the spots. Over time the spots may combine to enlarge to form blotches. Leaves may yellow and drop prematurely.

The organisms that cause leaf spots survive in fallen infected leaves and twigs. Some may remain in dead twigs on the tree. During wet weather, spores are released which may splashed or be windblown onto newly emerging tender leaves where they germinate in the moisture and infect the leaf. Overhead watering late in the day or during the night, heavy dews and close spacing of plants prolong wetting of the leaf surface and provide more opportunities for fungal or bacterial infections.

Live with the disease. Leaf spots are largely an aesthetic problem as few leaf spots seriously damage the host. Also control is seldom achieved after the infection has started.
Remove infected leaves and dead twigs. Raking up and disposing of infected leaves as they drop and pruning out dead twigs can help control the disease by removing spores that can re-infect the new leaves. This will not cure the problem but it can help minimize infections.

It is hard to tell from the picture IF it is ash or hickory. Ash trees have compound leaves with several leaflets. The compound leaf is attached so that they are opposite from each other. And the twigs and branches are attached opposite also. IF this is the case for your tree than it is ash. IF not it is one of the hickory trees. A close-up picture would help of the leaf attachment to the twigs.  

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Jim Hyland

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30 years experiance in the ID and management of forest diseases and ID of landscape tree diseases.

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