Phytophthora Leaf Blight of Hibiscus, a New Disease Caused by Phytophthora parasitica. Charles R. Semer IV, Technical Branch, Yoder Brothers, Inc., P.O. Box 68, Alva, FL 33920. Boligala C. Raju, Technical Branch, Yoder Brothers, Inc., P.O. Box 68, Alva, FL 33920. Plant Dis. 69:1005-1006. Accepted for publication 8 July 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-1005.

Phytophthora parasitica caused a severe leaf blight on cuttings and stock plants of several commercial hibiscus cultivars. Leaves of Crown of Bohemia and Pink Versicolor had water-soaked lesions surrounded by a chlorotic halo 3–5 days after inoculation. Lesions turned black, and white mycelium extended over the leaf surface. Isolations from leaves consistently yielded P. parasitica, and this organism caused typical leaf blight on inoculated leaves of six cultivars. The hibiscus isolate also was pathogenic to azalea (Rhododendron indicum ‘Prize’), chrysanthemum (Chrysanthemum × morifolium ‘Capri’ and ‘Vermilion’), Ficus benjamina, and Brassaia actinophylla. Several Phytophthora species were tested on hibiscus and found to cause leaf blight. Conditions favorable for symptom expression were temperatures of 20–22 C and 90–100% RH for 3–5 days.