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.