Sclerotinia (Sclerotinia sclerotior

Sclerotinia (Sclerotinia sclerotiorum) - Seed can
be contaminated with dormant survival structures
(sclerotia) of the pathogen:
The disease causes necrotic, light to bleached
lesions on leaves, petioles, and seed stalks.
Continuous expansion of a lesion on the stem can
girdle the stem, causing wilting and premature
plant death of the plant above the lesion. A white
cottony mold is commonly associated with the
expanding lesions. Macroscopic, black survival
structures called sclerotia are formed on and in
diseased tissues. Sclerotia of S. sclerotiorum can
survive in the soil for up to five years.
Germination of sclerotia leads to production of
airborne spores and/or fungal strands that infect
crown and foliar tissues. Symptoms typically are
first observed on petioles of the flowers that have
fallen and become trapped in the canopy (petioles
serve as a source of nutrition for the fungus), and
on leaves closest to the ground where the relative
humidity is higher. Small sclerotia inadvertently
harvested with seed, can contaminate seed lots
and act as an inoculum source for future plantings.
Rotate fields with non-hosts crops, such as
grasses, for at least 4 years. Irrigate early in the
day to provide sufficient time for plants to dry
thoroughly in the afternoon sunshine. Remove
infected plants prior to seed harvest.