Toxicity and Field Efficiency of Several Fungicides against Ustilaginoidea virens

The toxicities of 19fungicides and the mixture difenoconazole validamycin A against Ustilaginoidea virens were tested in laboratory by detecting mycelial growth rate,and eight fungicides with better efficacy were selected to test in fields.The results showed that propiconazole,trifloxystrobin,prochloraz,tebuconazole,picoxystrobin,azoxystrobin and difenoconazole had stronger inhibition on mycelial growth,and the EC50values were 0.025 4,0.032 8,0.041 8,0.045 1,0.082 6,0.100 1and 0.148 2mg.L-1,respectively.The mixture of difenoconazole and validamycin A combined with the ratio of 1∶2had obvious efficiency on Ustilaginoidea virens,with the 174.78 and the EC500.226 3 mg.L-1.Field tests revealed that 43% tebuconazole SC,25% azoxystrobin SC,25% prochloraz EC,8% validamycin A 4%difenoconazole WP and 25% propiconazole EC had better control effect,which were 83.27%,82.76%,82.73%,80.66%and 80.35%,respectively.