Cyazofamid (4-chloro-2-cyano-N,N-dimethyl-5-p-tolylimidazole-1-sulfonamide) is a novel fungicide with high levels of activity against Oomycetes fungi and Plasmodiophora brassicae Woronin. The effects of cyazofamid were investigated against P. brassicae, the causal agent of clubroot disease in Chinese cabbage. Cyazofamid at 0.3 mg litre(-1) inhibited resting spore germination of this pathogen by about 80%. Cyazofamid at 3-10 mg litre(-1) exhibited fungicidal activity to resting spores of P. brassicae 1-10 days after treatment. When cyazofamid was applied to infested soil, both root-hair infections and club formation caused by P. brassicae were strongly inhibited at 1-3 mg kg(-1) dry soil. These results suggest that cyazofamid directly inhibits resting spore germination, thereby leading to the inhibition of root-hair infection and club formation. Cyazofamid at 3 mg kg(-1) dry soil also exhibited complete control of clubroot disease. The effect of broadcast soil application using a dust formulation at 2 kg AI ha(-1) (equivalent to 1.3 mg AI kg(-1) dry soil), and plug seedling tray application by a suspension concentrate formulation at 200 and 400 mg AI tray(-1) (30 x 60 x 4 cm3) against P. brassicae was also evaluated. Cyazofamid exhibited good efficacy against the pathogen. The sequential treatment including plug seedling tray application with cyazofamid and pre-plant broadcast soil application with the fungicide fluazinam also exhibited excellent levels of control. These results indicate that cyazofamid has a high potential to be an effective fungicide for the control of clubroot disease.
Cyazofamid (ISO proposed common name), 4-chloro-2-cyano-N,N-dimethyl-5-p-tolylimidazole-1-sulfonamide is a novel fungicide exhibiting specific activity against diseases caused by Oomycetes. In tests, cyazofamid at 0.4-1.6 mg litre-1 exhibited excellent preventative activity against Phytophthora infestans on tomato and Pseudoperonospora cubensis on cucumber. Minimum inhibitory concentrations of cyazofamid against both diseases were over 63 times lower than those of mancozeb and at least 16 times lower than those of metalaxyl. Cyazofamid at 1.6-25 mg litre-1 exhibited not only preventative activity, but also stable residual activity and rainfastness. Cyazofamid at 6.3 mg litre-1 reduced zoosporangia formation of P infestans and P cubensis on host plants by 100 and 94% respectively. Cyazofamid also exhibited translaminar and curative activity. Cyazofamid has a new mode of action for fungicides and exhibits no cross-resistance with other currently registered and commonly used fungicides. These properties lead to a high level control by cyazofamid in field.
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