2019 Volume 2019 Issue 66 Pages 12-13
The symptoms of alternaria leaf spot and leaf blight diseases on welsh onion are similar and cannot be distinguished visually. To research the occurrence of these diseases, brown leaf spots appearing on welsh onions were collected from lower leaves in western areas of Shizuoka Prefecture every month from August to December in 2013, 2014 and 2015. Conidia on the spots were removed with cellophane tape and then observed for disease diagnosis under microscopic observation. The occurrence of alternaria leaf spot was lower than that of leaf blight at rates from 36.4% to 2.6%, except for 60.0% on September 2013. It was proved that the main pathogen of brown leaf spots was leaf blight in the western area of Shizuoka Prefecture.
