Evaluating the efficacy of osthole and matrine for control of Sorghum purple spot

Osthole is a coumarin compound extracted from the canopy flower of the umbelliferae. Matrine, whose main components are alkaloids and flavonoids, was extracted from the roots, stems, leaves and fruits of Sophora flavescens by ethanol or other organic solvents. In this study, the efficacy of the combined biological agents matrine and osthole against Sorghum purple spot caused by Cercospora sorghi was conducted by laboratory, greenhouse and field experiments. The results from petridish assay showed that the inhibitory effect of the mixture of osthole and matrine against C. sorghi was better than osthole or matrine alone or Zineb, and the best mixing ratio of osthole to matrine was 1:2. In greenhouse experiment, the efficacy of 25 μg/mL of matrine · osthole against Sorghum purple spot was similar to Zineb. Field experiment showed that the efficacy of 25 μg/mL of matrine · osthole on Sorghum purple spot reached 68.4% on the 30th day. These results suggested that the combined matrine and osthole had a good effect and could be used as an alternative fungicide against Sorghum purple spot.