Club root, also called swollen fingers and known by other names, is a severe fungal disease caused by a fungus called Plasmodiophora brassicae that lives in the soil. This disease affects certain plants by entering through their root hairs.
When plants are infected, their roots become swollen, deformed, and misshapen, often looking like clubs. These diseased roots can crack and rot, making it difficult for plants to absorb water and nutrients.
Affected crops often grow poorly and wilt during hot days but may recover during cooler nights.
Club root disease significantly reduces crop yields and can even lead to complete crop failure.
This disease primarily affects plants in the cruciferous family, including cultivated crops and weeds. It also affects a few other plants, which can be categorized as follows:
Most susceptible: Cabbage, Chinese cabbage, Brussels sprouts, certain types of turnips, and more.
Moderately susceptible: Kale, cauliflower, collards, broccoli, certain types of turnips and radishes, and others.
Less susceptible: Canola, black mustard, certain varieties of turnips and radishes, and others.
The fungus Plasmodiophora brassicae can survive in the soil for a long time, about 7-10 years or even longer, in the form of resting spores.
The disease develops more easily in soil with high moisture levels and temperatures between 18°-25°C. It is mainly associated with acidic soils. Once inside the roots of infected plants, the fungus grows rapidly, causing the cells to increase in number and size, resulting in the formation of “clubbed” roots. As the organism develops in the plant, it produces new zoospores that can infect the same plant or nearby plants, starting the cycle again. Eventually, resting spores are formed within the diseased plant tissue, and when the crop roots break down, these spores are released into the soil.
The disease is not transmitted through seeds, but the fungus can spread through runoff water, irrigation water, contaminated equipment, and to some extent, by wandering animals.
The primary way the causal agent spreads is through the use of contaminated transplants.
Clubroot can extensively affect the roots of plants even before any aboveground signs appear. The first noticeable symptom is abnormal wilting and yellowing of leaves, especially on warm days. If the soil is moist, these symptoms may only become apparent when water stress occurs.
If infection occurs early in the plant’s growth, young crops become stunted and may die. If infection happens later, the plants do not produce marketable heads or show proper growth.
When affected plants are pulled out of the soil, their roots are usually swollen and distorted.
The size of root deformities may vary, from small swellings on the main and side roots to large club-shaped roots, depending on when the plants were infected.
Apart from hindering water uptake, the clubbed tissue lacks a protective outer layer, making it vulnerable to other infections like soft rot.
Initially, plants infected with clubroot appear healthy, but as they grow older, they become weak, exhibit slow growth, wilt under sunlight, and remain stunted. The disease initially manifests in scattered groups of a few to several plants within the field. However, as seasons pass, the entire field may become infected.
To effectively combat the disease, it is recommended to apply systemic fungicides directly to the soil. Some fungicides suitable for this purpose include:
- CHANCETYL ELITE 800WDG
- TRINITY GOLD 452WP
- COLONIZER 440WP
- DOMAIN 250EC
- EXCEMPO CURVE 250SC
- GREEN COP 500WP
- GEARLOCK TURBO 250WP
- MILLIONAIRE 690WDG
- PYRAMID 700WP
- Whenever possible, choose plant varieties that have built-in resistance to the disease.
- Practice crop rotation, alternating with non-host crops for a period of 3-5 years.
- Ensure proper weed control, as weeds can harbor diseases.
- Carefully remove and dispose of infected plants.
- Sterilize garden tools after each use.
- Improve soil pH by adding basal fertilizers mixed with HUMIPOWER during application.
- Solarize the soil, which involves exposing it to sunlight to reduce or eliminate soil-dwelling pathogens.
- Always use disease-free planting materials.
- Take prompt action to control the disease.
- Rotate the use of different chemicals to prevent the fungus from developing resistance.
- Maintain proper crop nutrition to enhance overall plant health.