Black rot caused by Phytophthora nicotianae and Phytophthora palmivora on Cattleya wittigiana and Dendrobium thyrsiflorum in Brazil

Orchids are among the most cultivated flowers in the world. Plants of Dendrobium thyrsiflorum (DT) and Cattleya wittigiana (CW), cultivated at the Botanic Garden of Bauru in São Paulo, Brazil, presented black rot symptoms. The causal organism was identified as P. palmivora on DT and P. nicotianae on CW orchids based on its morphological and molecular characterization. Inoculation caused disease symptoms and Koch's postulates were fulfilled by re-isolation of the pathogen.