First Report of Downy Mildew of Salvia in Florida. R. T. McMillanJr., University of Florida, Tropical Research and Eucation Center, Homestead, FL 33031. Jr., and W. R. Graves, University of Florida, Tropical Research and Eucation Center, Homestead, FL 33031. Plant Dis. 78:03171. Accepted for publication 13 December 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0317C.
Commercial cultivation of garden sage, Salvia officinalis L., in Florida is limited to the Homestead area. In June 1993, 100% of plants in a 0.1-acre planting of sage were found to have typical symptoms of downy mildew. Diseased plants were dwarfed, measuring a few centimeters to 50-cm tall, compared with an adjacent block of disease-free plants that were 80-to 100-cm tall. Yellow spots appeared on the adaxial leaf surface and then turned brown. A grayish mold appeared on the abaxial surface. The fungus produced intercellular mycelia with filamentous and branched haustoria. Conidiophores were 440-540 Μm in length, with erect trunks di-chotomously branched five to seven times. Conidiophore branches were somewhat reflexed, and their sharp-pointed terminals bore single, elliptical brown sporangia measuring 18-21 x 21-26 ?m and lacked apical papillae. The fungus was identified as Peronospora lamii A. Braun. Experimental plants of S. officianalis were inoculated with a suspension of 2 ? 105 conidia per milliliter of P. lamii, placed in a growth chamber at 22 C for 3 days, and observed for symptoms after 5 days. Typical symptoms of the disease developed, and the conidiophores and conidia from leaf spots were in the range described for P. lamii. The disease has been reported on Salvia spp. in Iowa and Kansas, but this is the first report in Florida. Apparently the combination of temperatures from 10 to 23 C with early morning dew during the spring of 1993 was favorable for the development of downy mildew on Salvia.