Club-Root of Cabbage and Related Crops
Vegetable Disease Information Note 17 (VDIN-0017)
Charles W Averre, Extension Plant Pathologist

Club-root of cabbage and related crops is a serious disease in North Carolina because infested fields remain unsuited for production of cabbage and related crops for many years, and the fungus has a history of spreading to other fields in the community. This disease is probably the major reason for the decline of commercial cabbage production in some northwestern counties in North Carolina. It has also caused damage in gardens in other areas of the state, primarily in home gardens. Every effort should be made to avoid the introduction of the fungus in contaminated lots of transplants.

The disease is restricted to plants in the mustard family, both cultivated and weeds, and to a few other plants: corn poppy (Papaver rhoeas), mignonette (Roseda odorata), ryegrass (Lilium perenne), and red clover (Trifolium pratense). Cultivated crops vary in their susceptibility to the disease.

Very susceptible	Medium susceptible	Mildly susceptible or resistant
Cabbage, Chinese cabbage brussels sprouts, and some turnips	Broccoli, cauliflower, collard, kale, kohlrabi, rutabaga, turnip, and radish	Garden cress, mustard, some turnip and radish varieties, and stock

Symptoms and Characteristics

Infected plants at first appear normal, but as they mature, they become unthrifty, grow slowly, wilt during sunny days and become stunted. Usually the disease first appears in the field in scattered groups of a few to many plants. In successive seasons, the entire field may become infected. Affected plants have large galls or clubs on the roots and will produce a poor crop, or no crop at all.

The disease intensity is more severe if soils are wet during and after transplanting or seeding. Some soil types appear to be somewhat non-compatible for survival of the fungus; and in such soils, the persistence of the fungus in the absence of a host may be as short as three years. Preliminary observations suggest that poorly drained, sandy soils, low in organic matter, may be non-compatible, whereas well-drained clay type soils are compatible; and the fungus will persist for many years, ten years or more. The disease is not seed-borne. But, the fungus is readily spread in surface runoff water, irrigation water, contaminated equipment, and to some extent by roving animals. The use of contaminated transplants is the chief means of spread of the causal agent.

Causal Agent

The fungus of this disease is the soil-borne Plasmodiophora bassicae, an obligate parasite that can only live and cause disease in crops of the mustard family and four species in other families. There may be specialized forms (races) of the fungus that vary in the intensity of disease caused on different crops and ability to survive in different areas. The fungus produces resting spores that can remain alive for years in some soil types in the absence of susceptible crops.

Control

The practical control of this disease emphasizes avoiding the introduction of the fungus in a field. The importance of never planting contaminated lots of plants cannot be overstated. Once the disease is present in a farming operation, control measures are difficult, expensive, and not very effective. Resistant varieties of some of the crops have been reported, but are not acceptable for commercial markets.

Always use plants certified by the official state certifying agency. Plants from outside of North Carolina, by law, must be inspected by the North Carolina Department of Agriculture upon arrival. If even a trace of club-root is present on a few plants, or is known to be present in the plant bed, reject the entire lot.
Locate plant beds at sites without a history of club-root. Do not irrigate from sources that might be contaminated from cabbage fields.
Always decontaminate equipment after working in a field suspected of having the club-root fungus by thorough washing followed by spraying all surfaces with a disinfectant such as "Lysol," formaldehyde, etc.
Grow cabbage and related crops once every three to five years with crops not in the mustard family. For this rotation to be effective, it is necessary that susceptible weeds and volunteer plants (see section on Hosts) be excluded.
Broadcast and incorporate 1500 pounds of "quick lime" (calcium hydroxide) per acre just before planting or seeding.
For transplanting cabbage, cauliflower, broccoli, and brussels sprouts, use 6 pounds of Terraclor 75WP per hundred gallons of water per acre; use 3/4 pint per plant.

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Plant Disease Information Notes Home Page
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Recommendations of specific chemicals are based upon information on the manufacturer's label and performance in a limited number of trials. Because environmental conditions and methods of application by growers may vary widely, performance of the chemical will not always conform to the safety and pest control standards indicated by experimental data. All recommendations for pesticide use were legal at the time of publication, but the status of registration and use patterns are subject to change by actions of state and federal regulatory agencies. 08/91/1500

Published by North Carolina Cooperative Extension Service Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.

Reformatted Dec. 2000 by A.V. Lemay