Diagnosing sclerotinia stem rot in narrow-leafed lupins and field peas

Sclerotinia stem rot (Sclerotinia sclerotiorum ) is a fungal disease which infects most broad leaf crop and pasture species but not cereals. It is most common in higher rainfall areas and usually affects plants after flowering in warm and damp conditions.

 

Infected flowering spike and pods
Stem rot fungal growth and sclerote on stem
Sclerotes packed inside infected stems
Pod and seed infection

What to look for

    Paddock

  • Whole plants or branches that wilt and die in spring.
  • Lush, wet crops are most affected.

    Plant

  • Lesions occur in the upper half of the main stem, branches and on flowers and pods.
  • The fungus produces a white cottony-looking growth that girdles the stem, causing the plant parts above the lesion to wilt and die.
  • Individual pods or complete flower spikes can be completely covered by white fungal growth.
  • Hard black sclerotia, 2-8 mm in diameter, are produced in the fungal growth or in the cavities of infected stems or pods.
  • Harvested seed will be contaminated by sclerotia.

What else could it be

Condition Similarities Differences
Diagnosing sclerotinia collar rot in narrow-leafed lupins White cottony stem lesions, premature death Growth with embedded tiny sclerotia affects the stem base at soil level.

Where did it come from?

  • Sclerotinia survives as sclerotia (hard, dark resting bodies) in the soil for many years, and infects many broadleaf crops and weeds.
  • Canola is highly susceptible. Lupins and chickpeas are commonly infected whereas faba beans and field peas appear to be less susceptible.
  • During cool moist weather sclerotia near the surface germinate and produce small, cream, mushroom-like bodies containing many spores that are carried by wind to nearby crops.
  • Normally the spore must first germinate on, then infect, dead or dying plant material (such as flower petals) before it invades healthy tissues.
  • Infected petals that lodge between the stems and leaves are a major infection source. Cool, wet weather favours the disease and mists, dews and fogs provide enough moisture for infection.

Management strategies

Rotation
Rotation
  • Crop rotation can have some effect, although sclerotia survive for significant periods. Cereals are non-hosts and provide the most effective disease break.
  • Avoid sowing lupins in close rotation with other broad leaf crop species such as canola.
  • Foliar fungicides are not currently registered for sclerotinia in lupins.

Where to go for expert help

DDLS Seed Testing and Certification
+61 (0)8 9368 3721
Page last updated: Wednesday, 6 May 2015 - 3:25pm