Cabbage Integrated Pest Management : An Ecological Guide.

Major Diseases of CabbageManagement & control practicesPreventive activities:Most preventive activities as described for clubroot and black rot also apply for black leg disease (exceptfor the pH factors for clubroot). In summary:· Crop rotation: rotate both cabbage nursery and production field by not growing cruciferous cropsfor at least 3 years.· Use of clean seed: either certified by a reliable seed company, or treated seed. See section 3.3.· Use of clean transplants: Seedlings should not be transplanted from seedbeds that show anydiseased plants.· Avoid overhead irrigation. The splashing water may spread the disease.· Ensure good air circulation, drainage and rapid evaporation of dew, e.g. by wide spacing, orientingrows in the prevailing wind direction, choosing a sunny planting site, etc.· Sanitation: clean the field of old leaves and other crop left-overs before transplanting seedlings.· Diseased leaves should not be fed to farm animals if manure is to be used on crucifer fields:researchers report that manure from cattle fed on black leg debris is an important infection source!Once the disease is present in the field:· Remove infected plant material. Take it away from the field to a compost pile, or a place far fromthe production field.¤Points to remember about black leg:1. Black leg can cause “damping-off” type symptoms in seedlings and leaf spots in older plants.2. The fungus can survive on seed and in residue from diseased plants. Splashing water, fieldworkers, and wind can spread the disease.3. Sanitation (removing and destroying) infected plant material) is the main management practice.8.9 Physiological disordersPhysiological disorders are “diseases” caused by adverse environmental conditions. Major causes ofthese disorders are excessively high or low temperatures, soil-moisture disturbances, sun burn, pesticideburn (when the leaves of a plant turn brown-black when the dose of a pesticide is too high), nutritionaldisorders, and even air pollution.Fertilizer deficiencies (sometimes due to too low a soil pH) are a common cause of physiological disorders.If a plant is not supplied with sufficient amounts of the fertilizer elements it needs for good growthit will develop symptoms of lack of nourishment. These symptoms are specific for a crop and for afertilizer element. Deficiencies may often develop on light sandy soils that let rain water through easilyand allow nutrients to leach away. On the other hand, over-fertilization may also cause severe growthdistortions in plants.Some of the most common physiological disorders for cabbage are listed below. See also section 3.5.7.on fertilization needs of cabbage and box on deficiency symptoms for macro and micro nutrients insection 7.6Cabbage Ecological Guide - 2000170