Virulence Difference of Fungicides against Phytophthora capsici at Different Stages

The bioactivity of 9 fungicides against different stages of Phytophthora capsici was compared in vitro. The results showed that dimethomorph and flumorph had significant inhibitory effect on the 4 different growth stages of the target pathogen(P1319), with 50% effective concentration (EC50) values ranging from 0.14 to 0.61 μg/mL, and from 0.18 to 0.68 μg/mL,respectively, their 95% effective concentration (EC95) values lower than 3 μg/mL. Metalaxyl could significantly inhibit the mycelial growth and sporangium formation, however, it had no inhibitory effect against zoospore cyst germination and sporangium germination. Azoxystrobin and chlorothalonil strongly exhibit th e inhibition of the sporangium formation, zoospore cyst germination and sporangium germination, the EC50values were ranging from 0.03 to 6.15 μg/mL, and 0.07 to 1.97 μg/mL. Higher concentration mancozeb posessed inhibition on sporangium formation, zoospore cyst germination and sporangium germination, but without any activity on mycelial growth of P. capsici. Fosetyl-aluminium, p(ο)-butanoylphenol, and ο-allphenol showed weak inhibition at the 4 stages.