Cabbage Integrated Pest Management : An Ecological Guide.

Major Diseases of Cabbage8MAJORDISEASES OF CABBAGESUMMARYMajor diseases of cabbage in seedbeds are damping-off and downy mildew. In the mainfield, a number of other diseases can occur and cause yield loss which occasionally can besevere. Seldom will diseases in the main field cause total yield loss.Some general disease management practices are given here. Specific practices are listedunder individual disease sections.· Use of disease-resistant varieties. Cabbage varieties may vary in susceptibility to diseases.Check with seed companies and local extension offices for information. Setting upvariety trials to test how well particular varieties perform locally is recommended.· Increasing soil organic matter. This can increase soil microorganism activity, which lowerspopulation densities of pathogenic, soil-borne fungi.· Clean planting material. Use of clean seed such as treated seed (section 3.3) or “certified”seed that has been inspected for pathogens at all stages of production. Cleanplanting material includes healthy, disease-free transplants, also when bought from elsewhere.· Grow a healthy crop. A vigorous but balanced plant growth is the key! Fertilizer andwater management are important factors here. Some examples:v Fertilizer: using too much may result in salt damage to roots, opening the way forsecondary infections. Balancing watering and fertilizer is also important. The succulentgrowth of plants given too much water and nitrogen encourages certain pathogens.On the other hand, stressed plants, especially those low in potassium andcalcium, are more vulnerable to diseases.v water management: the most important practice is providing drainage to keep soilaround roots from becoming waterlogged to prevent rotting. It is also important thatfoliage stay dry. Infectious material or inoculum of water-borne pathogens spreadsfrom infected to healthy leaves by water droplets, and fungal pathogens need waterto germinate and enter the leaf. Water management methods are listed in section 3.9.· Sanitation. Removing diseased plants (or parts) will help prevent the spread of pathogensto healthy plants. Crop debris can be used to make compost. If temperatures duringcomposting rise high enough and are uniformly achieved in the pile by mixing, mostpathogensaredestroyed. Sanitation also includes weed control and insect control because manypathogens persist in weed hosts or are spread by insects.· Crop rotation. Rotate crops to disease-free fields to avoid buildup of pathogens in thefield. Rotation to an entirely different plant family is most effective against diseases thatattack only one crop. However, some pathogens, such as those causing damping-off androot rots, attack many families and in this case rotation is unlikely to reduce disease.· Use of biocontrol agents. Good results have been obtained with use of Trichoderma sp.for control of soil-borne diseases such as damping-off.151 Cabbage Ecological Guide - 2000