Clubroot

Clubroot is caused by the soil-borne fungus Plasmodiophora brassicae, and it is the most serious disease of the brassica family.

Physical Description

Species & Taxonomy

  • Kingdom: Rhizaria
  • Phylum: Cercozoa
  • Class: Phytomyxea
  • Order: Plasmodiophorales
  • Family: Plasmodiophoraceae
  • Genus Species: Plasmodiophora brassicae

Lifecycle

  • spores are released into the soil
  • can survive in the soil without a suitable host for up to 20 years REOG
  • disease is spread on infected plant material and contaminated soil REOG

Plants Affected

 

Plants Unaffected

  • Brassicas (broccoli, cabbage, kale, cauliflower, mustards, radish): clubroot is the most serious disease of brassicas
  • wallflower
  • stocks
  • candytuft

Geographical Range

 

Signs & Symptoms

Whole Plant

  • stunted growth
  • eventual plant death
  • wilt on hot sunny days, but may recover at night REOG
  • plant growth and crop yields are severely reduced REOG

Leaves

  • leaves start to discolor
  • red tint may develop on foliage REOG

Flowers

Fruit

Roots/Tubers

  • roots develop swollen galls (either a single large gall, or several smaller swellings) REOG

How to Positively Identify

 

Treatment

  • spores can survive 20 years dormant in the soil
  • there is no cure
  • solarization probably doesn’t help, if the fungus doesn’t get killed in a hot compost pile (140°F)
  • burn or dispose of diseased plants and soil surrounding the plant (do not compost)

Prevention & Control

This disease is very difficult to control, so avoidance is very important

Cultural Controls:

Habitat:

Temperature & Humidity:

  • it is less of a problem in hot, dry seasons REOG
  • less of a problem in spring-maturing crops REOG
  • it thrives in damp, acid conditions REOG

Mulching & Cultivation Practices:

  • buy transplants from a reliable source, or raise your own
  • build up good soil fertility and improve drainage REOG
  • lime acid soils: alkaline soil (pH at or above 7) discourages clubroot
  • remove infected plants as soon as possible, preferably before the galls start to disintegrate REOG
  • do not compost infected plants REOG
  • practice good garden hygiene (clean implements, gloves and shoes; move cuttings and prunings to compost or disposal right away)

Natural Enemies & Biological Controls

Insects:

Animals:

Reptiles:

Barriers

Traps

Sprays & Dusts

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Sources:

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