Survey and pathogen identification of rhubarb diseases in Gansu province.
Objective: To investigate diseases occurring in Rheum palmatum in Gansu province and identify pathogen. Method: Field survey in the main R. palmatum producing area and the pathogens were identified on the base of morphology. Result: Eight fungal diseases have been found after disease surveys on R. palmatum in Gansu province from 2004 to 2007. They were leaf smut (Thecaphora schwarzmaniana), leaf spot (Septoria sp.), rust (Puccinia rheipalmati), ring spot (Ascochyta rhei), powdery mildew (Erysiphe polygoni.), grey mold (Botrytis sp.), root rot (Fusarium oxyxporium) and a virus disease. Conclusion: Leaf smut, a severe disease with the incidence of 14%-26%, is the urgent problem waiting to be solved effectively. Powdery mildew and grey mold were reported for the first time in China.