Sclerotinia stem rot: biology
Sclerotia are long-lived in the soil. When surface soil moisture is high for prolonged periods (usually not until the crop canopy has closed) sclerotia germinate to produce golf tee-shaped apothecia. Apothecia release air-borne spores which land on petals and infect plants when the petals fall. Some infection occurs as in sunflower.
Sclerotinia sclerotiorum life cycle
The fungus overwinters in the soil and on stubble in storage bodies called sclerotia, which can remain viable for five years or longer. When conditions are favourable, some sclerotia will germinate while others remain dormant.
Germinating sclerotia can infect canola plants two ways:
- By producing mycelia that directly infect plants they come into contact with.
- By producing apothecia, spore producing bodies with a mushroom-like appearance that occur at the soil line.
One sclerotium can produce up to 15 apothecia, each of which can release millions of spores. Those spores can survive for up to 21 days, and easily travel significant distances on the lightest of breezes. They land on canola petals where they germinate. When infected petals drop and are caught in the branches of the crop, the entire plant is put at risk.
