Disease Note.

Occurrence of Powdery Mildew on Parsley In California. S. T. Koike, University of California Cooperative Extension, Salinas 93901. G. S. Saenz, University of California, Berkeley 94720.. Plant Dis. 78:1219. Accepted for publication 24 August 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-1219D.

In 1993, commercial parsley (Petroselinum crispum (Mill.) Nym. ex A. W. Hill) grown in both San Joaquin and Salinas valleys exhibited symptoms and signs of a foliar disease. Symptoms consisted of chlorosis and crinkling of leaves. The characteristic white fungal growth typical of a powdery mildew was present on all infected leaves. Mycelium was am-phigenous and in patches. Conidiophores were straight; foot cells were cylindrical, followed by a longer cell and one or two shorter cells. Appressoria were lobed. Conidia were produced singly and were 34–44 x 13–16 aem. Fibrosin bodies were not observed. Germ tubes were located at the ends of the conidia and formed clavate appressoria. The fungus was identified as Erysiphe heraclei DC (1,2). Cleistothecia were not present. Pathogenicity was established by gently pressing diseased leaves of the San Joaquin Valley sample against adaxial sides of leaves of 2-mo-old parsley plants. Twenty plants of both plain leaf (cv. Italian Plain) and curled (cv. Extra Curly) cultivars were inoculated. Inoculated plants were incubated in a moist chamber for 48 hr and then maintained in a greenhouse. After 4 wk, powdery mildew developed on both cultivars and symptoms were identical to those of diseased plants collected from commercial fields. For cv. Italian Plain, 12 of 20 plants became infected; for cv. Extra Curly, 5 of 20 plants became infected. This is the first report of powdery mildew on parsley in California. While the source of inoculum is unknown, E. heraclei is observed on another host, carrot (Daucus carota L.), which is grown extensively in the same area of the Salinas Valley as parsley.