Phytophthora heterospora is the causal agent of black rot disease on the orchid Cattleya leopoldii in Brazil.

Widely produced and marketed worldwide, orchids suffers from several diseases that have a negative effect on production. Black rot disease is among the most common and severe disease, characterized by black spots of rot on leaves, pseudobulbs and roots, which usually lead to the plant death. The world literature lists some Phytophthora species as causal agents of the disease, but there is no advanced study on the etiology of this disease in Brazil, which makes it difficult to determine an efficient control method. This work aims to contribute to the study of the etiology of black rot on Cattleya leopoldii in Brazil. Severely diseased C. leopoldii plants with typical symptoms of black rot, collected from a commercial orchid farm in Brazil, were taken to the laboratory and used to isolate the pathogen. Based on morphological characters analysis combined with molecular data, the isolates were identified as belonging to the species Phytophthora heterospora. This is the first worldwide report of P. heterospora causing black rot disease on orchids.