Inhibitory activities of six fungicides against mycelial growth and conidial germination of Alternaria alternata

Activities of six different fungicides(flusilazole, iprodione, dimethachlon, azoxystrobin, kresoxim-methyl, carbendazim) to Alternaria alternata were determined by mycelial growth rate method and conidial germination assay. The results showed that the six fungicides showed different inhibitory activities against A. alternata on mycelial growth and conidial germination. The most effective fungicide against the mycelial growth of A. alternata was flusilazole, with average EC50 value of(0.34±0.11) mg/L, followed by dimethachlon (1.13±0.68) mg/L and iprodione (2.08±0.24) mg/L. The most effective fungicide against theconidial germination of A. alternata was azoxystrobin in combination with 100 mg/L SHAM, with average EC50 value of(0.28±0.09) mg/L, followed by azoxystrobin (5.79±2.76) mg/L, kresoxim-methyl (11.93±3.93) mg/L, dimethachlon (19.95±15.94) mg/L and iprodione (23.33±11.33) mg/L when used alone. Carbendazim showed the lowest inhibition on both mycelial growth and conidial germination of A. alternata, suggesting it should not be used for controlling tobacco brown spot. Further study is needed to investigate the field control efficacy of iprodione, flusilazole, azoxystrobin and kresoxim-methyl against tobacco brown spot.