First report of Lasiodiplodia euphorbiaceicola and Neoscytalidium dimidiatum causing dieback on Cattleya spp. (Orchidaceae) in Brazil

The orchid trade is a significant global industry, with annual sales of approximately USD 2 billion. Orchids rank among the most important potted plants sold in Brazil. Cattleya is one of the most widely cultivated Brazilian orchid genera, with some species threatened with extinction. Despite their economic relevance, the etiology of many orchid diseases remains unknown. One of these diseases is the pseudobulb dieback observed in Cattleya species in orchid nurseries in Goiânia municipality, Goiás state in Brazil. Symptomatic plants of C. amethystoglossa, C. guttata, and C. nobilior exhibited necrosis at the pseudobulb apex, premature leaf drop, and downward lesion progression. Isolates were morphologically identified as belonging to Neoscytalidium (Botryosphaeriaceae) and Lasiodiplodia (Botryosphaeriaceae). To confirm the disease etiology, pathogenicity tests were performed with each isolate. Multilocus phylogenetic analysis identified four isolates as Neoscytalidium dimidiatum (from C. amethystoglossa), N. dimidiatum (from C. guttata) and two isolates of Lasiodiplodia euphorbiaceicola (from C. nobilior). All isolates induced dieback symptoms, and reisolations confirmed pathogenicity, fulfilling Koch’s postulates. This is the first report of L. euphorbiaceicola worldwide and N. dimidiatum in Brazil causing dieback disease in Cattleya spp.