Sclerotinia sclerotiorum on Phaseolus vulgaris bushbean

Sclerotinia sclerotiorum on Phaseolus vulgaris bushbean

© Rasbak

Type: Diseases


Sclerotinia fungus (white mould) (Sclerotinia spp.)

This genus of fungi includes Sclerotinia sclerotiorum, Sclerotinia minor, and Sclerotinia trifoliorum which between them can infect most of the crops grown on allotments. They get their common name from the cotton wool-like mould which attacks the above-ground parts of the plant, often killing it. As the fungus grows it may form small (2-5mm by up to 25mm) blackish sclerotia. These hard little irregularly shaped pods are what allows the fungus to survive between crops. When conditions are right, they either produce miniture toadstool-like structures which release millions of spores, or begin sending out new cotton wool-like growth to infect nearby plants. The fungus prefers cool, damp conditions which help the spores to germinate and symptoms generally don't appear until summer.

Symptoms

  • Initially, wet, slimy patches appear on particularly near the base of the stem
  • Plants may suddenly wilt and collapse
  • Lower leaves turn brown and soggy
  • Cotton wool like growth on any aerial part of the plant
  • Affected parts may develop a bleached and/or shredded appearance

Prevention & control

  • It thrives in cool damp conditions so good ventilation is important
  • Good hygiene - remove and burn affected plants
  • Don't plant susceptible crops in the same soil for up to five years
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