Cabbage Integrated Pest Management : An Ecological Guide.

Major Diseases of CabbageSource and spreadThe bacteria survive in soil on decaying and dead plant debris. Wounds are the most common entry pointfor this bacterium. The infection can occur through surface areas like leaves injured by insects or mechanicalmeans or through damaged roots or stems. Bacteria spread through the veins to other plant parts.Some species of maggot fly are known to carry the soft rot bacteria. Eggs of the flies are laid in decayingcabbages and as the egg hatch, the larvae become contaminated with the soft rot bacteria. Infested adultflies lay eggs smeared with soft rot bacteria on maturing cabbage. The emerging larvae serve as vectorsas they feed on the cabbage and create wounds that allow the bacteria to infect the plant tissue.Role of environmental factorsWarm wet conditions promote disease development. Abundant moisture at the surface of the planttissue, where wounds are present, is essential for invasion. After infection has taken place, fairly highrelative humidity is needed for progress of the disease. When decaying cabbages are placed in a dryatmosphere, the rotted tissue dehydrates rapidly and further advance of the disease may be checkedcompletely.Soft rot can accompany mineral deficiency symptoms. Potassium deficiency or an unbalance of potassiumand other essential nutrients may bring about leaf scorching which may be followed by a bacterial attack.Soft rots are also common where an excess of farmyard manure is applied on poorly drained soils,probably due to the maggots attracted by the manure, as explained above.Importance - plant compensation - physiological impactSoft rot is mostly a problem shortly before the harvest period, when cabbage heads near maturation.Usually, the disease is very localized, only a few heads here and there drop out due to soft rot. In warm,wet conditions, the bacteria progress inside the plant and eventually, the whole cabbage head will berotten. Plant compensation does not take place at this stage. Often, farmers will quickly harvest headswith soft rot and peel off the outer affected leaves. The small remaining head may still be used forconsumption.Natural enemies/antagonistsUnknown.Management & control practicesPrevention activities :· Sanitation practices: make sure the field is clean from crop debris from a previous season. Also theborders of the field should be cleaned from crop debris.· Avoid injury to the crop - the wounds can be entry points for the bacteria.· Monitor field regularly and remove heavily infected heads from the field.· Crop rotation is probably of limited value for Erwinia because it can survive in the soil for many yearson dead plant tissue.Once an infection is present in the field:· Lightly infected heads can be harvested and the affected leaves peeled off. Those heads can still besold or used for home consumption.Cabbage Ecological Guide - 2000158