What Now? Tar Spots On Maple Trees, These Are Fun-guys Only

I have seen those dark spots in the summer on the Red Maple, and they are nearly invisible on the dark leaves – only if you look closer. However, in the fall they are too visible so I couldn’t resists to find out what it was. A contrast of black spot on yellow leaves does not make a pretty maple tree.


I am sure that by now everyone heard about the Asian Long-Horned Beetle, the Emerald Ash Borer and Yellow Headed Spruce Sawfly infestations. The latest and greatest is the borer and the sawfly. Borer is an invasive insect that kills all different species of healthy ash trees. The sawfly feeds only on the spruce trees. I guess we are missing a natural predator for those insects.

The classic scenario I experienced on my backyard was the infestation of ladybugs. This was few years ago and once in the while I still find one or two of those nasty ladybugs in my house. Since the ladybug population decreased over few years I do find more aphids in my garden. Releasing ladybugs, a predator to aphids, is one of few natural methods to control garden aphid infestations.

Then this one I will never know. About three or four years ago we were driving on Hwy 404 to work. It was just before Hwy 7, for about five minutes of driving we saw dark funnel clouds on top of many trees, no not tornadoes. It wasn’t like only one or two trees, it was hundreds of trees. What kind of bug it was I have no idea.

May be someone will after reading this post.


So what is going on with Red Maple trees on my street?

I was able to narrow down my search to the tar spots. Black spot, also called tar spot, on maple leaves are caused by fungi in the genus Rhytisma (whatever it is? my Latin isn’t that good anyway). Leaves usually become infected in the late spring or late summer and may fall off prematurely. These tar spot are not usually detrimental to the maple trees.

In our case here, it is already November and the leaves are falling due to natural fall cycle. Some are still hanging to the tree even with these spots.


And the treatment is? The fungus winters-over on leaves that have dropped to the ground. The leaves need to be raked up in the fall otherwise the spores will reappear in the spring on the old leaves and spread to any nearby tree. Well, we definitely have the spread on all trees, but everyone been raking them and composting. Hopefully it will go away.

Treating your maple tree is usually not effective. You cannot just treat one tree, you have to treat them all in the neighborhood, and for now raking is the solution.