First report of leaf blight and petiole rot of carrot caused by Rhizoctonia solani AG-1 IB

Carrot plants with leaf blight and petiole rot were found in Hokkaido, Japan, in September 2016. The causal fungus, identified as Rhizoctonia solani anastomosis group (AG)-1 IB, caused leaf blight and petiole rot on carrot but not root rot in inoculation tests. We also confirmed that it can be discriminated on the basis of symptoms and pathogenicity from the pathogen R. solani AG-2-2 IV, which causes carrot root rot. This is the first report of leaf blight and petiole rot of carrot caused by R. solani AG-1 IB.