Cornell University

When strawberries go bad

Rhizopus stolonifer is an awesome mold. You’ve probably seen it before, on the peaches in your fruit bowl, or on your bagel, or (hopefully not) attacking your body. It’s a versatile and ubiquitous thing, and it makes great hairy colonies that grow astonishingly quickly.
Here is it causing a post-harvest disease of strawberries. You’re seeing seven days of growth and subsidence.

Quicktime 5+ movie

Time lapse video of delicious strawberries inoculated with the evil mold Rhizopus stolonifer by Kent Loeffler.

The little hairs that seem to be clawing their way up are the sporangiophores. If you squint a bit you can almost see a little grey pinhead (sporangium) atop each one. Those pinheads are filled with fungal spores, each hoping to find its very own strawberry.

  • DoctorFungus has a good discussion of Rhizopus spp. implicated in nasty, invasive human disease (zygomycosis). In general, don’t worry about catching a fungal infection from rotten fruit. However, if your immune system is not working right because of HIV or immune-suppressing drugs, be wary of fungi.
  • Rhizopus oligosporus, a friendlier cousin of the strawberry mold, is used to produce tempeh. You know, tempeh, that meat-like substance made from fermented soybeans. Buy some from your local grocer or health food store and stir fry it up for dinner.
  • The strawberries? No, don’t eat them once they’ve become hairy.



20 Responses to “ When strawberries go bad ”


Most people don't pay much attention to fungi, which include things like mushrooms, molds, yeasts, and mildews. Here at Cornell we think they're pretty fascinating. In fact, even the most disgusting foot diseases and moldy strawberries are dear to our hearts. We'd like to talk to you about fungi, so that like us, you too can tell gross stories at the dinner table. Afterwards, maybe you'll notice some things you would have overlooked before, and we think this could be good for the planet.

Kathie T. Hodge, Editor

Beneath Notice, our book of borescopic mycology.


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