There is an exception, according to the University of Wisconsin-Madison horticulture department. If your trees have serious foliar fungal diseases, you should be raking your leaves. “While most leaf spots on leaves are cosmetic and harmless to the overall health of the tree, fallen diseased leaves do serve as a source for spores that can infect next year’s emerging leaves,” according to a post from the school. “Significantly diseased leaves should be raked and removed from the area and disposed of properly, such as by burying, burning where allowed, or hot composting.”
University Communications