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The Rotting of the Harvest

Michelle Grabowski, UMN Extension Educator

Storage vegetables are a great way to keep eating healthy and local throughout Minnesota's long winter. A wide variety of vegetables will keep for one to several months with minimal preparation. Common storage vegetables include carrots, beets, parsnips, turnips, cabbage, kohlrabi, potatoes, onions, garlic, winter squash and celeriac.

Under ideal conditions winter squash can keep for 2-6 months (depending on variety), onions keep up to 4 months, potatoes keep up to 6 months, and carrots keep up to 8 months. It is important to remember that each vegetable has specific moisture and temperature requirements to maintain them in good condition during storage. In her publication 'Harvesting and Storing Home Garden Vegetables', Dr. Cindy Tong of the University of Minnesota Department of Horticulture, provides a detailed table on what environmental conditions each vegetable requires. In addition, Dr. Tong talks about different places in the home that these conditions could be found or created.

Photo 1: Dark, soft, sunken spots on this pumpkin are the early stages of storage rot.
M. Grabowski, UMN Extension.

Whether you grow vegetables in your own garden, receive them as part of a CSA, or purchase them from the farmers market, always select undamaged produce for storage. Small wounds are easy entry points for storage rot fungi and bacteria. Produce with even a small area of rot will continue to rot and can spread the pathogen to neighboring produce in the refrigerator or on the pantry shelf.

Storage rot fungi often infect vegetables while they are growing in the field, but symptoms may not show up until weeks later in storage. The 2010 growing season had regular rains and warm weather. These are ideal conditions for fungal plant pathogens. Many common garden vegetables suffered from severe leaf spot and fruit rot diseases in the field. It is likely that even healthy looking vegetables put into storage contained some unseen latent infections.

It is important to inspect storage vegetables regularly through the winter. At this time of year, fungal rot can frequently be found in storage vegetables, particularly those in less than ideal conditions. Look for soft sunken spots or dark discolored areas on the surface of the vegetable. Fluffy white cottony growth is an indication of fungal activity and can often be found at the stem end or base of the vegetables, where two vegetables touch together, or areas where humidity is high. Powdery black, blue green or even pink fungal spores may been present.

Photo 2: Fusarium basal rot on shallot.
M.Grabowski, UMN Extension.

If early signs of rot are found, these vegetables should be immediately removed from the storage bin. If caught early enough, rotted areas can be cut out and the remaining healthy tissue can be used for dinner. If left, however, these minor infections can grow until the vegetable completely collapses from rot. In many cases the disease will spread to infect and rot neighboring vegetables. It is possible for an entire bin of vegetables to succumb to rot started on one fruit.

If you do not have ideal vegetable storage facilities in your home, look for stores that carry local Minnesota storage vegetables. Often these vegetables are labeled with the Minnesota Grown label.

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