Sat, 24 Aug 2013 00:14:32 GMT — You might have noticed those dark spots covering the leaves on some of the trees in your yard and around town lately. They would have appeared as small yellow blemishes in early June. They've continued to grow and darken through the summer season and by now they've become unsightly dark spots that look like tar.It's an infection of the leaf that typically affects several varieties of maple trees. It's caused by a fungus called Rhytisma, more commonly known as black tar spots. Rhytisma spores are easily spread from tree to tree through the air. The fungus seems to thrive in damp environment, much like the one we've had so far this summer.While the fungus is not aesthetically pleasing, the good news is it's not harmful. That's according Doctor Bob Heyd, forest health specialist with the Michigan Department of Natural Resources."He says the leaf is perfectly productive and producing food for the tree. This is not a stressing event for the trees, in fact, very few times do we see any stress created by the fungus."However, by the end of summer, the tar spots can make the tree look ragged and unkempt. In extreme cases, tar spots can also cause leaves to fall prematurely, cutting short the time we get to enjoy all those epic fall colors.If the tar spots become too much for you, there are a couple management strategies. There are fungicides that have proven effective. However, they need to be applied in early spring and several times throughout the summer. That may prove difficult if you have large trees.The best remedy is to simply rake your fallen leaves regularly. You should either burn or compost them so that the fungus spores do not spread to other trees in your neighborhood. This will also go a long way in preventing the fungus from spreading next spring!
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