North America

Coming to terms with Fusarium dry rot in potato storages

Potato specialists in the US recently published an information fact sheet on Fusarium dry rot in potato storages in which they provide practical tips on how potato growers can deal with this all too familiar problem that is no doubt known to many potato growers in North America. The bulletin was published in the Northwest Potato Research Consortium’s newsletter Potato Progress.

Kasia Duellman, Don McMoran, Debra Inglis and Kenneth Frost say that Fusarium dry rot is caused by various species of fungi in the genus Fusarium, including F. sambucinum (the most prevalent species in the Pacific Northwest), F. coeruleumF. avanaceumF. equiseti and others that have been associated with dry rot symptoms from samples recently collected as part of a project funded by the Northwest Potato Research Consortium.

The pathogens require a wound in order to cause infection, and such wounding can occur any time tubers are handled, such as during harvest or when being moved into or out of storage. Symptoms include internal darkly pigmented, dry rotted tissue that may expand and result in hollowed-out tubers. White, yellow or pink-colored fungal growth is sometimes seen associated with the dry rot lesion.

The specialists point out that managing Fusarium dry rot in storage requires a multi-faceted approach, with many steps occurring many weeks before tubers enter storage. In addition to cleaning and disinfecting storages and adjusting harvesting and handling equipment, implementing cultural practices to minimize bruises or other wounds is necessary. 

Today, few chemical options are available for post-harvest dry rot management in storage. Disinfectants, such as phosphorous acids, hydrogen peroxide/peroxyacetic acids  or chlorine dioxides have not been shown to consistently manage dry rot in storage, and many disinfectants are inhibited by organic matter. 

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The specialists say that in preparation for planting, growers should use certified seed with as little dry rot as possible. (Keep in mind that dry rot pathogens are nearly always found in seed lots to some degree.) Growers should handle seed carefully to minimize wounding and promote healing after transporting and cutting/treating.

Read the full bulletin here