Cabbage Integrated Pest Management : An Ecological Guide.

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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
Major Diseases of Cabbage8.1 Damping-off in seedbeds (Fusarium, Rhizoctonia, Pythium, Phytophthora sp.)Causal agents : fungi – Fusarium, Rhizoctonia, Pythium, Phytophthora sp.A number of species of soil-dwelling fungi, including Fusarium, Rhizoctonia, Pythium and Phytophthorasp., infect vegetables, especially legumes, crucifers and solanaceous crops. Species of Pythium aremore common than the others. If the infection occurs either before (pre-emergence) or just after emergence(post-emergence), and development of a spot (lesion) at the soil line results in collapse andshriveling of the plant, the disease is called ‘damping-off’.Signs and symptomsInfection occurs just around the soil line in young seedlings. Damping-off fungi rarely attack transplantsin the field or established seedlings.The symptoms of this disease are brown, water-soaked areas around the lesion that shrivel and pinchthe seedling off at the base. The dry rot is usually limited to the outer part of the stem and infected plantsmay fall down or may remain more or less upright. Infected plants remain under-developed and usuallydie.Pre-emergence damping offStem rot(from Kerruish, 1994)Source and spreadThe fungi are natural soil inhabitants but when circumstances are favorable and when susceptible hostplants are present, the population can increase to damaging levels. It is difficult to predict when that willoccur: it depends on temperature and humidity but also on the population of microorganisms in the soil.Sometimes, there are microorganisms (antagonists) that serve as natural enemies of the pathogens:they can keep the population of the pathogen under control.Infection occurs through wounds or natural openings but Pythium can also actively penetrate the tendertissue near root tips.In case of Pythium infection, dying seedlings contain the spore-carrying structures of the fungus. Thespores can drop to the soil (and attack seed or young seedling roots), or be carried by wind or spread toanother location by surface water or irrigation water. Pythium can be transported in soil attached toseedling roots during transplanting. And Pythium can form thick-walled spores (called oospores) thatcan survive during adverse conditions and persist for several years in the soil.Cabbage Ecological Guide - 2000152
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Why this guide?About this guideThis
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Introduction1.4 Cabbage: a bit of h
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Cabbage Crop DevelopmentPresently t
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Cabbage Crop Development2.2 Suscept
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Major Agronomic Practices3MAJOR AGR
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Major Agronomic Practices3.2.3 Seed
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Major Agronomic PracticesUse protec
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Major Agronomic Practices3.4.2 Soil
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Major Agronomic Practicesthan 7, th
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Major Agronomic Practices3.4.7 Soil
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Major Agronomic PracticesSome of th
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Major Agronomic PracticeslllCreates
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Major Agronomic PracticesWhen a com
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Major Agronomic PracticesIn additio
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Major Agronomic PracticesSome farme
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Major Agronomic PracticesEffects of
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Major Agronomic PracticesAn example
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Major Agronomic Practicesseed beds,
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Major Agronomic Practicesthis layer
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Major Agronomic PracticesPotting se
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Major Agronomic PracticesTransplant
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Major Agronomic Practices3.9 Water
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Major Agronomic PracticesHowever, w
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Major Agronomic PracticesSome examp
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Ecology of Insect Pests and Natural
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Major Cabbage Insect Pests5MAJOR CA
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Major Cabbage Insect PestsDiadegma
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Major Cabbage Insect PestsTrap crop
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Major Cabbage Insect PestsThe sad s
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Major Cabbage Insect PestsPlant dam
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Major Cabbage Insect PestsJ Free bi
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Major Cabbage Insect Pestsbeetles.
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Major Cabbage Insect Pestsinstars f
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Major Cabbage Insect Pests¤Points
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Major Cabbage Insect PestsSome NPV
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Major Cabbage Insect PestsAdults ar
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Major Cabbage Insect PestsThe adult
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Major Cabbage Insect PestsLarval de
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Page 142 and 143: Disease EcologyThe disease triangle
Page 144 and 145: Disease Ecologygrowth malformations
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Page 148 and 149: Disease Ecologycontaminated seeds :
Page 150 and 151: Disease EcologyTrichoderma species
Page 154 and 155: Major Diseases of CabbageRole of en
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Page 168 and 169: Major Diseases of Cabbage8.7 Downy
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Page 172 and 173: Major Diseases of CabbageNitrogen (
Page 174 and 175: Weed Management9WEEDMANAGEMENTSUMMA
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Page 178 and 179: Weed Managementcompost or it may be
Page 180 and 181: Weed Management· Check details of
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Page 184 and 185: Rodent ManagementRats are a common
Page 186 and 187: Rodent Management10.4 Rat managemen
Page 188 and 189: Rodent Management10.4.4 Biological
Page 190 and 191: Key to Some Common Cabbage Insect P
Page 192 and 193: Literature and Internet Reference L
Page 200 and 201: PESTS & DISEASES COMMON TO CABBAGEP
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Plate 3Fig. 13 : Advanced symptoms
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deficiency symptoms ---------------
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