First Report of Corynespora Leaf Spot of Thyme in Florida. R. T. McMillan,Jr., University of Florida. Tropical Research and Education Center, Homestead 33031 . W. R Graves, University of Florida. Tropical Research and Education Center, Homestead 33031. Plant Dis 79:1186. Accepted for publication 24 August 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-1186D.
Leaf spots that ranged from brown, necrotic specks to brown target spots (1 to 3 mm in diameter) with halos were observed on small (6 cm tall) garden thyme (Thymus vulgaris L.) plants from a commercial shade-house in June 1994. Conidia of Corynespora cassiicola (Berk. & M. A. Curtis) C. T. Wei were observed in lesions on both upper and lower leaf surfaces. The fungus was isolated on corn meal agar (Difco, Detroit, Mich.) where it did nol sporulate abundantly Disease-free thyme plants were inoculated with 4-mm-square hyphal blocks on Ihe upper surface of the leaf. The inoculated plants were gently misted with a hand sprayer, bagged in a 2-mil polyethylene bag, and placed in a greenhouse with an ambient temperature of 28 to 34°C. Typical target spot lesions developed after 14 days on (he healthy inoculated thyme plants. Corynespora cassiicola was reisolated from lesions on these plants. This is the first report of C. cassiicola on thyme in the Florida and the United States.