Cabbage Integrated Pest Management : An Ecological Guide.

Major Diseases of CabbageOnce there is an infection in the field:vuproot infected plants including all roots and destroy them but.....:· do not throw the infected plants at the side of the field. From there, the spores will be releasedinto the soil and may spread into the field again. The result: you have helped spread the disease!· do not put uprooted clubroot plants on a compost pile. When the temperature inside the compostpile is not high enough (above 60 o C), the spores will not be killed and may be spread intothe field again with the compost. Temperatures above 60 o C should kill the spores inside acompost pile, but it is difficult to tell whether the temperature inside the pile reached that level fora sufficient period of time.· uprooted clubroot plants should not be fed to farm animals as the spores are so strong that theycan survive passing through stomach and intestines. As a consequence, spores will be spreadwith the manure of the animals.· leave infected plants to dry for some time and burn them. It’s the safest way to be sure to haveremoved the spores.· unfortunately, by uprooting a diseased plant, the disease is not removed from the soil. Thefungus is still present in the soil area around that infected plant. By removing the infected plant,you have only accomplished that the disease will not spread further.vvvvvCheck the pH, if it’s too low, apply lime to raise it. Applying wood ashes also helps to raise pH. Theinfection will be less with a pH of around 7.When the soil is very heavily infected with clubroot, consider growing another crop. Even after applyinglime, it may still take several seasons before the pH has risen enough to suppress clubroot.Soil sterilization: several trials were done, for example in the mountain areas of the Philippines, totest if solarization would control clubroot. High soil temperatures (over 60 o C), due to heating up of thesoil under the plastic sheets should kill spores of the fungus. The results of the trials varied considerably,therefore, no recommendation for use of this technique is given in this guide. It may however,be interesting to try in a small area of an infected field, but preferably combined with liming the soil.See section 3.7.1.2 and 3.4.6.Applying fungicides is not effective to control this fungus. This is first of all because the spores arevery strong and may still be inside the plant roots. Secondly, the fungus can be located deep in thesoil and where pesticides may not reach.Chitosan, a naturally derived component (polysaccharide) from the outer skeletons of crab, mayhave potential for clubroot control. Chitosan has been shown to be effective for control of Sclerotiniarot (caused by Sclerotinia sclerotiorum) of carrots (Cheah et al. 1997). In studies with Chinesecabbage in New Zealand, it significantly reduced the club weights.¤Points to remember about clubroot :1. Clubroot is a fungal disease that causes enlargements (the “clubs”) on the roots, resulting inwilting of the plant during warm days and small head sizes or none at all.2. Clubroot is spread by soil particles, by transplants and by drainage water. Transplants areusually the main means of widespread distribution.3. Resistant varieties, use of clean transplants, removing weeds, raising soil pH to7 or above, andproper sanitation practices are ways to prevent or reduce clubroot infection. Soils (severely)infected become unfit for cultivation of crucifers. Trichoderma may become a biocontrol option inthe future.Cabbage Ecological Guide - 2000166