Club Root
Plasmodiophora brassicae
Club Root, Clubroot
Knolvoet bij bloemkool (Plasmodiophora brassicae on cauliflower)
by Rasbak. CC-BY-SA-3.0
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
Loss of fine roots
Distorted swellings on the plant roots
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
Practise good hygiene. Regularly clean gardening tools, including shoes and wheelbarrows!
Brassicas should be grown in an alkaline bed.
Make sure beds are well-drained.
Do not transplant Brassicas from locations other than your land.
If it's known that the disease is present, sow your own Brassicas in sterile compost and use those to transplant.