. Bulletin. Natural history; Natural history. Diseases of Fruit Trees, 1922-1928 489 nual prevalence of per cent, and an average annual index of fruit intensity amounting to per cent., this disease is annually a menace to cherry production. Leaf spotting of cherry trees, as may be seen in Table XXI, al- ways has a high prevalence. In 1932 its prevalence index was per cent., in 1931 it was per cent., and in all other years except. Fig. 27. Scale for measuring the intensity of spotting on plum leaves In each example the area of the spots is expressed as a percentage of the
. Bulletin. Natural history; Natural history. Diseases of Fruit Trees, 1922-1928 489 nual prevalence of per cent, and an average annual index of fruit intensity amounting to per cent., this disease is annually a menace to cherry production. Leaf spotting of cherry trees, as may be seen in Table XXI, al- ways has a high prevalence. In 1932 its prevalence index was per cent., in 1931 it was per cent., and in all other years except. Fig. 27. Scale for measuring the intensity of spotting on plum leaves In each example the area of the spots is expressed as a percentage of the area of the leaf. This scale measures roughly the combined intensity of the bacterial shot-hole and coccomyces leaf-spot lesions. 1935, for which we have no adequate data, it was computed to be 100 per cent. Its prevalence in Illinois, as exemplified by our data for six years, averages annually per Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Illinois. Natural History Survey Division. Urbana, State of Illinois, Dept. of Registration and Education, Natural History Survey Division
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