Thursday, 10 June 2010

How to cope with clubroot

  • Clubroot is a common disease of cabbages, radishes, turnips and other plants belonging to the family Cruciferae (mustard family). 
  • It is caused by Plasmodiophora brassicae, which was once considered a slime mould but is now put in the group Phytomyxea. It has as many as nine variants. 
  • Gall formation or distortion takes place on latent roots and gives the shape of a club or spindle.
  • In the cabbage such attacks on the roots cause undeveloped heads or a failure to head at all, followed often by decline in vigor or by death. 
  • It is an important disease, affecting an estimated 10% of the total cultured area worldwide.
  • The organism produces cysts that remain in the soil until a suitable host is available to infect, starting the cycle again. 
  • The cysts can live for 8 or 9 years so normal rotations are of little use in eliminating the problem.
  • Soil may remain infected for 20 years; 
Symptoms
  • The first sign is a wilting of plants, especially in dry weather. 
  • The plants fail to develop well and often fail to develop a crop. 
  • Examining the roots you will notice swellings and roots that look knobbly, like advanced arthritis which is where the old colloquial name of 'fingers and toes' comes from.
  • Although no chemical controls are available to the gardener nowadays, the good news is that some resistant varieties are coming onto the market and more are being developed.
Non-chemical prevention
If you must continue to grow brassicas on infected land then steps to avoid introduction include:
  • good drainage
  • rotation
  • liming acid soils to a pH around 7
  • working in high levels of organic matter ensuring clean plants are used - source must be known to be free of disease (best grown at home in sterile medium) 
  • boots and tools used on infected land must be thoroughly cleaned before use on clean land
  • Once infected avoid growing any brassicas except fast maturing types such as Texsel greens or cut and come again oriental seedlings. 
  • If you have no other land available, and you must grow types with a lengthy growing season, you can try sowing seed in modules, and potting up until the plants reach a height of 10cm (4") before planting out. A root drench may also help.
Organic approach
  • As a preventative against clubroot, boil rhubarb leaves in water and pour into holes before planting seeds.
  • A variation is to drop a square inch of rhubarb leaf into the planting hole before hand.
  • Another variation is to cut a 1” cube of Rhubarb, cut into 2 equal portions and place them at the bottom of the hole into which you intend to plant your Brassica plant with the cut side up.
  • Yet another variation is to place a stick of rhubard with attached leaf on the ground between the new planys, changing them as they deteriorate.
Chemical approachs
  • Armillatox
  • Some commercial growers use agro-chemicals that are not available to the general public.
  • However, on sale to the general public, Armillatox has in the past claimed that their product would "clear out" club root & onion white rot and kill both ants & weevils. 
  • The company had to drop this claim under pressure from Brussels and the product is now called "Armillatox Patio Cleaner".
  • It is reputed that the product sold today is exactly the same as it was when the above clubroot claims were being made. 
  • With this in mind the following quote is from the old Armillatox sales literature. 
We believe that the correct long term answer to club root is to purge the ground free of this parasite, and this can be done by drenching the soil with diluted Amillatox 50 parts of water to 1 part concentrate. If you have not been able to treat the ground prior to planting then a 100:1 dilution direct into the dibber holes plus the occasional watering at 150:1 every 3 weeks or so around the base of the plants will be beneficial. 
  • No need to lime the area as Armillatox will correct ph levels.
  • No need to use herbicides as Armillatox will sterilise weed seeds.
  • No need to fertilize as Armillatox will make up the deficiencies.
As this is a natural product made from phenols and blended in vegetable oil soap, it is completely bio-degradable, it is claimed that it will enhance the soil rather than polute it. These phenols are obtained from plant life and it is the phenols in growing plants that give them their natural resistance to disease.
  • We have not yet tried out this chemical approach, and would be interested to hear from anybody who has experience of it.

  • Jeyes Fluid
  • In the past, non-organic types have used dilutions of concentrated Tar Oil or Jeyes Fluid to treat the soil at the backend of the season.
  • Both of these products were banned a few years ago by the EU for use in the cultivation of food crops.
  • For decades Jeyes Fluid was used to sterilise the soil annually in UK greenhouses, until the EU ban.

1 comment:

  1. Thanks for sharing, Chin MW, http://www.ycglobalent.com

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