Marssonina blight is a common fungal disease that impacts the foliage of aspen trees. It is particularly bad this year due to the wet weather we experienced in May and June. Symptoms include brown/black spots (often surrounded by a yellow halo) on the leaves and premature leaf drop. Preventive fungicide sprays offer some control, but there are no curative measures. Infected leaves should be raked up and disposed of to minimize the number of fungal spores present.
Photo accredited to: J. Guyon II, USDA Forest Service