Clubroot management of highly infested soils

Clubroot (Plasmodiophora brassicae) is a disease that causes severe damage to cruciferous crops in Brazil. This study aimed to evaluate the chemical control of clubroot disease using flusulfamide at different concentrations compared with quintozene, chlorothalonil and pH reduction using lime. The efficiency of the chemical control and pH reduction combined with solarization was also tested in a commercial field. Three experiments were conducted using cauliflower cabbage and Chinese cabbage in fields located in Quatro Barras County (Parana State, Brazil) to determine the efficacies of flusulfamide, quintozene, chlorothalonil and lime. A fourth experiment was performed using broccoli with various combined control methods (pH reduction with lime, chemical control using flusulfamide and physical control with soil solarization in a factorial design). The fresh weight (g), commercial units and gall severity in the roots were evaluated. The quintozene, chlorothalonil and lime treatments, when applied alone, were not effective in controlling clubroot. The best treatment was flusulfamide at a rate of 20 L ha(-1) for the three studied species. The combination of lime to reduce pH with solarization and flusulfamide was effective to control clubroot and can be recommended to treat soils highly infested with P. brassicae. (C) 2012 Elsevier Ltd. All rights reserved.