CONTRIBUTED ABSTRACT
Major foliage fungus diseases of the seven major tree genera by Robert L. Tate.
Foliage fungus diseases of shade trees were classified symptomatically in five categories: 1) leaf spots, 2) leaf blights, 3) powdery mildews, 4) sooty molds, and 5) blisters. Seven genera of trees have been selected for this study. Each comprises more than 5% of the total and together account for 82% of all trees planted in the Northeastern United States. Each genus was then further divided into its most widely planted species and/or clones to facilitate a more accurate analysis of specific diseases. Acer, the most frequently planted genus (37% of the total) had the highest number of leaf-spotting diseases. However, none of these was considered to be serious when compared to the leaf blights. Gleditsia, the next most frequently planted genus (11 % of the total) was least affected by foliage diseases although one serious leaf-spotting fungus was noted. Foliage diseases do not appear to mar the tree. Quercus (9% of the total) and Platanus (6% of the total) are the genera most seriously affected by various leaf blights and powdery mildews. Leaf spots are of secondary importance. Tilia (8% of the total), while most seriously affected by a leaf blight, has been occasionally subjected to serious attacks by powdery mildew. Fraxinus (6% of the total) is affected by two major leaf-spotting diseases, one of which is extensive on younger trees. Malus (5% of the total) is most seriously affected by apple scab, a leaf blight. Powdery mildew is sometimes considered to be a major foliage disease.
Foliage diseases of shade trees do not rank in the same order of importance as do stem or root diseases because they rarely express themselves in complete defoliation. However, the overall effects of foliage diseases on tree vigor and survival may be much greater than has been realized. More effort should be put into measuring those effects. Department of Horticulture and Forestry, Rutgers University, New Brunswick, New Jersey.
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