With our wetter weather this year we have had a lot of issues.  It is hard to identify from the picture and without knowing what growing practices have been applied.  If there is just a spot here or there, I would not worry.  If a large percentage of the foliage have these spots, please bring a sample into our office located at 2775 Hwy 50 in the Mesa County Fairgrounds.  We are at the West end of the large parking lot.  Open 8-5, M-F.

At this time of year, the foliage is one its way out pretty soon so we don't worry too much unless it is widespread.  You can clean up your leaves when they drop in fall to help prevent the issue from coming back next year.