Club Root

Plasmodiophora brassicae

Club Root, Clubroot

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A plant infected with Clubroot Plasmodiophora brassicae
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Club Root is a disease that affects members of the Brassicaceae family exclusively. It causes large swellings and distortions to the roots that in turn rot and can cause the plant to die. It was originally thought to be a primitive fungus and then thought to be protozoa now we know it is caused by a phytomyxea which is somewhere in between the two.

Identification

Early infection is difficult to notice as it may be some subtle wilting during the day that recovers at night. In severe infections, however, the plants may be stunted and take on a purple tinge. They can also topple over and die. What causes this is the swelling and distortion of roots. In the later stages, this swelling and distortion cause the roots to rot into a foul-smelling mass. Similar symptoms can be caused by weevil larva. To distinguish, cut open the swollen root. Club Root should be solid all the way through whereas weevil larvae will hollow it out following feeding, with the small grubs evident in the soil.

Growth factors

Acidic soil

Symptoms

Wilting of top-growth during the day.
Stunted growth
Purple tinge to topgrowth
Toppling and death

Biological treatment

There are no treatments for this.

Chemical treatment

There are no treatments for this.

Lifecycle

Club Root is neither a fungus nor a bacterium and so has an odd lifecycle. It stays as resting spores in the soil until conditions are met where it germinates to produce swimming swarm spores that seek out roots where they enter through the root hairs. Once inside the roothairs, they produce a different type of swarm spore until the hair bursts and the swarm spores infect other parts of the root causing the swelling and distortion. Resting spores are then produced in the swellings to be released into the soil. Clubroot is a common disease of Cabbages, Broccoli, Cauliflower, Brussels Sprouts, Radishes, Turnips, Stocks, Wallflowers and other plants in the Brassicaceae family.

Prevention

Growing brassicas in an alkaline bed. Do not transplant Brassicas from land that it is unknown if it has the pathogen. Alternatively, sow your own brassicas in sterile compost and use those to transplant.

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