Thoughts for Food #16

Food for Thought:  Potato late blight 

LateBlightDo you know what caused the Irish potato famine in the 1840s and 1850s?

Did you know these problems caused massive hunger, distress, and resulted in mass emigration from the region for many years?

Did you also know that this disease can still be a concern if not properly managed?

And that the fungus which caused the Irish potato famine is still attacking!  It can cause serious problems for potato, tomato, eggplants and other solanaceous crops today.  Phytophthora infestans (appropriate name since it “infests”) is the cause of potato late blight; it is a fast moving, community disease, which growers (as well as home gardeners and garden center managers) must take seriously and manage properly to ensure a healthy, adequate food supply.

The growers in the Central Sands region of Wisconsin are using innovative pest management techniques to combat this very persistent fungus.  First, growers ensure that all seed is clean and disease-free to prevent the introduction of the fungus into the fields.  By WI state law, any growers, homeowners and/or garden centers are required to get rid of any signs and sources of late blight before the start of the growing season and ensure that any and all left over potatoes are destroyed of by April 15th each year.

Next, growers use a sophisticated weather and disease forecasting model that indicates when in the season growers should begin applying crop protectant materials to limit late blight from developing in fields.  This forecasting model ( Blightcast,) calculates disease severity values, which accumulate when conditions are right for disease development, usually  during high temperatures, high humidity and rain.

Since late blight can cause devastation to the crop throughout the whole region, growers will proactively destroy large portions of fields if late blight it found.  This is the only effective way to stop the disease from spreading; growers will lose more if they let it spread to other fields and neighboring locations. Growers also worry spreading the disease themselves as they move from field to field and routinely clean and sanitize all equipment , even their own boots, before entering  fields to avoid spreading the fungal spores.

Since late blight is a community disease, growers actively discuss late blight occurrences with regional growers, home garden centers, neighboring growers and home gardeners.   UW-Madison Plant Pathologist Amanda Gevens sends out state-wide updates on when to expect problems and then alerts growers to what locations the disease has been documented and how severe the outbreak is.  She actively discusses late blight concerns with local media to ensure that the general public is aware of the potentially devastating effects of this serious disease; gardeners are encouraged to destroy garden areas quickly if infection is found to protect other homeowners and local farmers. In recent years, the late blight fungus has been imported into Wisconsin on tomato plants sold in local garden centers and farmers markets, so it is critical that the public is aware of late blight.  We must realize that this is a community-wide problem, which requires everyone who grows plants that can host late blight to be watchful and ready to act!  Our food security is too important to be placed at risk by failing to act quickly when danger threatens. The Irish had little knowledge of what the disease was in the 1800s and no weapons to fight it and the resulting famine had tragic global consequences. The disease is still with us but science has now provided us with the tools to fight it and it is essential that everyone in the community joins the battle.

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