AVRDC International Cooperators'
Fact Sheet

Crucifer Diseases
 

Clubroot
Plasmodiophora brassicae

Found worldwide; most damaging in temperate regions
and tropical highlands

 severely affected cabbage root
 
Damage Symptoms

Most crucifer crops are susceptible to clubroot; cabbage, Chinese cabbage, and Brussels sprouts are highly susceptible. Enlargement of fine roots, secondary roots, and the taproot results in the formation of spindle-shaped clubs. The clubs are generally widest in the middle and taper toward the ends. Severely clubbed root systems are impaired and cannot efficiently absorb water and nutrients; therefore the plants are stunted and may wilt with only slight water stress. Lower levels frequently turn yellow in advanced stages of disease development.

clubroot on horseradish

Spindle-shaped clubs on lateral roots of horseradish

Conditions for Development

Resting spores can survive in the soil for at least 10 years, and can persist on cruciferous weeds indefinitely. The pathogen can be disseminated by soil contaminated equipment, in soil water, and by way of infected transplants. The disease is favored by acidic soils and infection can occur at soil temperatures between 10 and 32°C. The pathogen is composed of numerous pathotypes which have hampered efforts to breed cultivars with durable resistance.


Control

Use of disease-free transplants is most important in a disease management program. Crop rotation is impractical in most cases because the resting spores survive for such a long time and weed hosts can maintain the inoculum. Liming soil to raise the pH to 7.2 is very effective in reducing disease development. Use of fungicides in transplant water can also reduce disease development. Resistant cultivars must be tested in each location because of the many pathotypes of the pathogen.

Last updated: 2001. 
Information from: Vegetable Diseases: A Practical Guide. Lowell L. Black, AVRDC.

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