Sclerotinia

Sclerotinia diseases cause major loss in many horticultural crops (e.g. lettuce, beans, carrots, brassicas and peas).

Intense cropping and the use of Sclerotinia susceptible crops in rotations have led to a build up of Sclerotinia in soil. This factsheet outlines new control options that can assist with disease control when combined with other measures.

• Resting Sclerotinia bodies can survive for 5 years or more
  
  
• Biofumigant green manure crops and crops more tolerant to Sclerotinia infection should be used to reduce and prevent build-up of Sclerotinia
  
  
• New fungicides offer a suitable replacement for procymidone, recently withdrawn from use
  
  
• Better application, timing of fungicide sprays and the right volume of water is essential for effective disease control.

There are two species of Sclerotinia that cause concern:

S. minor usually infects through mycelium that comes in contact with lower leaves and stems. On rare occassions it also produces aerial spores.

S. sclerotiorum usually infects through aerial spores landing on fl owers and senescent or damaged tissues. The fungus spreads from these infected fl owers or tissues to healthy leaves or stems.

Sclerotia of S. Sclerotiorum can also produce mycelium, which can directly infect lower leaves and stems. In some places the pathogen is more aggressive under hot and humid conditions (eg Queensland). Wet conditions favour disease development of both species and they can both cause disease on brassica crops (watery soft rot).

Both species produce resting bodies (sclerotia) on infected tissue, which can survive in soil for up to 5 years (S. minor size up to 3 mm, S. sclerotiorum 5 - 15 mm). S. sclerotiorum requires humid conditions to develop the fruiting bodies (apothecia) that produce aerial spores. S. sclerotiorum also infects carrots (soft rot), green and dry beans (white mold) and many other horticultural crops.