Tests of fungicides against Alternaria brassicicola and studies on some factors enhancing attack by the fungus

SUMMARY When various fungicides were sprayed on detached cabbage cotyledons in the laboratory and on young plants in the glasshouse, propineb and mancozeb at 0·2 % a.i. consistently gave good protection against subsequent infection by spores of Alternaria brassicicola. Copper oxychloride, zineb, thiram and maneb showed promise in the laboratory, but were less successful in the glasshouse. Two fentin compounds were active at low concentrations against the fungus but were phytotoxic. Increased pathogenicity of A. brassicicola in the presence of cabbage pollen and of downy mildew infection in the laboratory is reported.