Diseases caused by fungi and bacteria
Bacterial speck is a bacterial disease and results in small, black spots on leaves, stems and fruits of tomatoes, at all stages of growth. It is most common from winter to mid spring. Copper hydroxide may give some control.
Clubroot is a fungus disease that only affects Brassicas (the broccoli family). Plants are yellowish and stunted, with large malformed ‘clubbed’ roots. Clubroot may be severe in warm weather. Avoid growing brassicas in the same area for four years and lime the soil if it is acidic.