Cabbage Integrated Pest Management : An Ecological Guide.

Major Diseases of Cabbagefluorescens) and fungi (e.g. Streptomyces griseoviridis, Trichoderma sp. and Gliocladium catenulatum)that control Rhizoctonia sp. These antagonistic organisms are available as biocontrol products registeredto control Rhyzoctonia and related soil-borne disease in the United States. Some of these products maybecome availabe in Asia in the future. (www25; www29)Management & control practicesSee section 8.1, damping-off. The same practices apply for bottom rot.¤Points to remember about bottom rot :1. Bottom rot is caused by a soil-borne pathogen that survives on decaying and dead organicmatter in the soil. The same fungus also causes damping-off in seedlings.2. Bottom rot occurs in areas with poor drainage or areas with a previous history of the disease.3. Optimizing drainage and growing conditions, using vigorous seed and transplants, crop rotation,and sanitation practices (removing crop debris) are ways to prevent disease problems.4. Good control of bottom rot can be achieved with use of the antagonistic fungi Trichoderma sp.There are many other effective biocontrol products which may become available in Asia in thefuture.8.5 Leaf spotCausal agent: several fungiLeaf spots on cabbage can be caused by several fungi. Each fungus can cause slightly different symptomsand the pathogen can sometimes only be distinguished with a microscope, which is usually not availablein the field. The most common leaf spot fungus is Alternaria brassicae, which is described below. Otherfungi causing leaf spot on cabbage include Mycosphaerella brassicicola, Phoma lingam (see section8.8) and Cercospora sp.In the field, the difference between the various fungal leaf spots is not always easy to make, especiallywith early symptoms. Note that for a proper decision on the management of fungal leaf spot, it is notalways necessary to be able to distinguish the different causal organisms. Most fungal leaf spots willneed the same management practice, mainly reduction of the source of infection by sanitation.Alternaria leaf spot - Alternaria brassicaeSee plate 2 Fig. 9This fungal disease is also known as black mold, gray leaf mold or blackspot.Causal agent: fungus – Alternaria brassicaeSigns and symptomsSymptoms of Alternaria leaf spot usually appear on the older leaves of the cabbage plant. The spotsbegin as black pinpoint-size spots and enlarge to distinct, brown-black leaf spots of 1 to 2 cm diameterwith concentric rings and sometimes a yellow area around the spot. The concentric rings contain theCabbage Ecological Guide - 2000160