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Plant Diseases/black spots on my sugar maple tree


Maple trunk2
Maple trunk2  

maple trunk1
maple trunk1  
Hi, this spring we noticed black spots and stripes on the main trunk of our sugar maple tree.  It almost looks like someone took a blow torch and burned spots (or a can of black spray paint) on the trunk and one of the main limbs. I'm attaching a picture of the bark so you can see the affected area.  We're worried it's some kind of fungus.  We have two swings on the tree, and my kids spend all summer climbing it so I'm wondering if we injured it.  What do you think it could be?  Thanks in advance for helping us save the family "climbing tree"!  Chris

It could be a couple of things. Borers (an insect) will infest the trunk of maples and sap will spill out onto the bark making the bark dark or black. There is also a disease called a bleeding canker that would look like this.  

Borers can be treated with an insecticide called Merit. This is sprayed on the trunk and will kill the insect under the bark. Borers attack trees under stress so I would fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb. per inch of trunk diameter scattered around the tree and watered in good. Apply the fertilizer just before a rain event and you will not need to water.

Bleeding cankers are a disease but not much in known about there control. Chemicals do not seem to work. The best thing is keep the tree healthy so fertilizing would be the best option.

So in both cases I would fertilize and to make sure it was not a borer I would recommend spraying with the Merit.

Check with your local garden type store for the insecticide and the fertilizer. Make sure you do not use a lawn fertilizer called Weed and Feed -- this contains a herbicide that will damage and/or kill trees.

Increasing the overall health of the tree will allow the tree to over come these problems.  

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Jim Hyland


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

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