Again, the problem is worse when spring weather is wet and cool. It is similar to leaf spot because once it is really noticeable, it is too late to do anything. Anthracnose looks like small spots on leaves that appear to be water-soaked, Goodspeed explains. These spots, which are usually found along the veins, enlarge and eventually turn red, brown or black. It spreads to the petiole of the leaf, and can eventually infect small twigs and branches.
Severe cases defoliate the tree and cause some twigs and smaller branches to die.
In addition to applying a fungicide now, the leaves should be raked up and destroyed in the fall. If possible, keep sprinklers away from the foliage of these trees to keep the leaves as dry as possible. Some sycamores are just too big to spray unless you hire a helicopter to do the job. Normally anthracnose and leaf spot are not fatal diseases, even if left untreated. Fire blight, however, can be fatal, Goodspeed warns.