Cercospora Leafspot of Photinia serrulata

Abstract

In the early stages, the lesions first appear as indefinite chlorotic spots, 1-2 mm in diameter, on both the upper and lower leaf surface. Soon the spots change to purple, increase in size to 2 to 25 mm in diam? eter, and finally become dark brown (Fig. 1). On the under surface of the leaf the spots are lighter brown in color and more indefinite in outline. The central portion of the spots on either leaf surface may appear downy or velvety due to the presence of large numbers of conidio? phores and conidia. Soon after the spots develop over a large portion of the leaf, abscission takes place and partial defoliation of the plant results. Lesions on the new growth usually begin to appear early in June, and the disease increases in severity as the summer progresses so that, by the end of October, the plants are severely defoliated with only small tufts of leaves at the terminal portions of the shoots. The cause of this disease was found to be an apparently undescribed species of Cercospora. This fungus is here described and named.