Pathogen Identification and Fungicide Evaluation for Sclerotinia Stem Rot of Gerbera jamesonii

  Objective   The pathogen of sclerotinia stem rot, a major disease of Gerbera jamesonii cultivated in Fujian, was identified. Effective fungicides that could be alternatively applied to curtail drug resistance were evaluated.

  Method   The causative pathogen of sclerotinia stem rot was isolated from tissue of the diseased plant and verified by Koch’s rule as well as morphological observation and ITS sequence of the microbe. Toxicities of selected fungicides were determined in the laboratory.

  Result   The isolated strain, C4-1, was identified as the culprit to be Sclerotinia sclerotiorum. Among the fungicides, hymexazol with an EC₅₀ of 0.032 4 μg·mL⁻¹ was most potent in inhibiting the pathogen growth. It was followed by boscalid with an EC₅₀ of 1.033 7 μg·mL⁻¹, dimetachlone with an EC₅₀ values of 1.8362 μg·mL⁻¹, triadimenol with an EC₅₀ of 6.9408 μg·mL⁻¹, and carbendazim the least effective agent with anEC₅₀ of 22.434 9 μg·mL⁻¹.

  Conclusion   S. sclerotiorumwas isolated and identified as the pathogen that caused the sclerotinia stem rot disease on G. jamesonii in the province. Of the fungicides evaluated, hymexazol, boscalid, and dimetachlone, could be used alternatively for the disease control to minimize drug resistance by the pathogen.