Clubroot

Symptoms by part

Causes

• Acidic soil conditions with a pH below 7.0.
• Poorly drained or waterlogged soil.
• Warm soil temperatures during the growing season.
• Presence of the pathogen in the soil from previous infected crops.

Could be confused with

• Cabbage root fly · Cabbage root fly larvae tunnel into the roots and cause decay, but they do not create the large, tumor like galls characteristic of clubroot.
• Root knot nematodes · These cause small, bead like galls on the roots rather than the massive, irregular swellings seen with clubroot.

Treatment

1. Remove the entire affected plant, including as much of the root system as possible, as soon as you notice wilting or stunted growth.
2. Dispose of all infected plant material in the trash, never in your compost pile.
3. Clean all gardening tools that touched the soil with a stiff brush and water to remove any clinging dirt before using them elsewhere.

Without chemicals

• Raise the soil pH to 7.2 or higher by adding garden lime, which makes the environment inhospitable to the pathogen.
• Improve soil drainage by adding organic matter or creating raised beds.
• Practice a long crop rotation of 6 to 7 years, avoiding all brassicas in the affected area during that time.
• Grow brassica seedlings in pots of clean, sterile potting mix before transplanting them into the garden.

Preventing it

• Test your soil pH regularly and add lime to keep it alkaline.
• Ensure all new plants are free of root galls before putting them in the ground.
• Avoid moving soil from an infected area to a clean part of the garden on your boots or tools.
• Control weeds in the brassica family, such as shepherd's purse or bittercress, as they can also host the disease.

When to act

Act immediately upon seeing stunted or wilting plants to prevent the pathogen from spreading further through the soil. If a plant is heavily infected, remove it entirely and do not attempt to save it.

Questions people ask

Can I compost plants that have clubroot?

No, you should never compost infected plants. The resting spores can survive the heat of a standard home compost pile and will spread the disease when you use the compost elsewhere.

How long do clubroot spores stay in the soil?

The resting spores are very resilient and can remain viable in the soil for up to 20 years, which is why long rotations and pH management are so important.

Will adding lime cure an infected plant?

No, lime will not cure a plant that is already infected. It only helps to suppress the activity of the spores in the soil for future plantings.

Plants it affects

• Spring Cabbage