Toxicity Measurement of Six Fungicides against Peony Root Rot Disease

[Objective] The aim was to screen out effective chemicals to control root rot disease. [Method] The relative inhibition rate of six kinds of fungicides at 1 mg / L against root rot disease were tested by the hypha growth rate in lab,meanwhile their toxicities were also measured.[Result]Under 1 mg/L,99% hymexazol had the highest relative inhibition rate( 93. 50%) against Phyllosticta commonsii; secondly was 50%carbendazim,with the relative inhibition rate of 89. 63%; the relative inhibitory rate of 50% thiram was 20. 00%. 99% hymexazol had the best toxicity to peony root rot disease,and its EC50 value only was 0. 002 7 mg / L; the followed was 50% carbendazim,and its EC50 value was 0. 019 5mg / L; the EC50 of 50% methyl· zinc·Thiram WP was 19. 134 6 mg / L. [Conclusion] These results provided the basis for controlling root rot disease in field.