London plane trees are losing leaves prematurely at this time. The following is more information.
London plane trees are losing their leaves prematurely and after a close look they have powdery mildew and a leafspot that produces circular non-descript brown spots on the leaves. The spots are numerous and both diseases are contributing to early defoliation. The fungus leafspot is Phyllosticta leafspot and is typically a weakly pathogenic fungus but the cool, wet weather has been ideal and with the trees senescing anyway, the fungus has been very aggressive. Fortunately, it will not cause a decline in overall tree health at this point in the season but is making the trees appear untidy. No fungicide sprays are recommended for this disease at this time.
London plane trees.
Information from Bob Mulrooney, Extension Plant Pathologist, UD.