White mold aka Sclerotinia sclerotiorum

Tue. Oct. 11, 2016

Click below to listen to my Garden Bite radio show:  White mold aka Sclerotinia sclerotiorum

Nope, not a “sexy” subject.  However, it’s been prevalent this year with all the rain and it’s not desirable.  So, what is it and what to do about it…

zinnias-with-white-moldOur friends at the University of Minnesota Extension have written an article on this stuff.  Click HERE for the full details.

White mold, Sclerotinia sclerotiorum, is a plant disease caused by the fungus I won’t even attempt to pronounce. This pathogen is capable of infecting over 400 plant species! Flower garden favorites like zinnia, petunia, salvia, and snapdragon are highly susceptible to white mold.

petunia-with-white-mold In the vegetable garden, tomatoes, green beans, lettuce and cabbage can all be infected. The removal of infected plants is a critical management strategy for this fungal foe.

Plant pathologists say the pathogen can survive up to 8 years in specialized resting structures produced on infected plant material.  Seriously?!?!  Infected plants often wilt and die. The lower stems will be tan and dry. If the humidity is high, white fluffy clumps of fungal growth may be seen on the stems. Gardeners may also see small, rough, black structures that look like seeds or peppercorns forming along stems or inside of them.  Those are the “resting structures” that will can live in your soil for years.  They reproduce yearly!

More on White Mold from the American Phytopathological Society

White mold on beans
White mold on beans

If you’re seeing white mold in your gardens, now’s the time to remove those plants before they settle in for winter and pop back up next year.  The entire plant should be removed as soon as possible. Infected plants can be composted IF the pile heats up to a minimum temperature of 148 degrees F. Alternatively infected plants can be deeply buried (6-12 inches below ground) in an area of the yard that will not be used for flowers or vegetables in the future like a mulched area around trees or shrubs.


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