First report of Pilidium concavum causing leaf necrosis on Fallopia japonica in the United States.
Several potted JKW plants in an outdoor study at the Oregon Department of Agriculture, Salem developed leaf spots. Samples collected on August 20, 2007 were sent to the FDWSRU for identification of the disease. The necrotic leaf spots were brown and large, 1 to 3 cm in diameter, and in some cases occupying 30% of the leaf area. Artificial inoculation of 15 plants was made on 2 occasions with a suspension. Symptoms similar to those in the original sample developed within 2 months after inoculation. The fungus was easily reisolated, and conidia from each type of conidioma produced similar growth on artificial media and similar disease after inoculation. The characteristic s of conidial size and disticntly different conidiomata are diagnostic of Pilidium concavum. A sequence of the ITS1-5.8-ITS2 region DNA extracted was found identical to that of P. concavum from Rosa sp. (BP 1107275; GenBank Accession No. AY487094), using a BLAST. This isolate, FDWSRU 07-116, has been deposited in the US National Fungus Collection (BPI 883546) and at the Centraalbureau voor Schimmelcultures (CBS 132725). This is thought to be the first report of P. concavum causing disease on a member of the Polygonaceae in North America.