The potato processor J.R. Simplot recently issued a warning to growers warning them to watch out for pink rot as they start harvest.

“If you know there’s rot in there, tell your harvest operator, ‘when you come to that low spot, pick up the harvester, drive over, and don’t harvest those certain areas’,” Scott Graham, Simplot’s raw agronomy manager, said, cited by the Manitoba Co-operator.

This is crucial, the expert says, because pink rot-causing fungi can grow and spread in the bunker through contaminated soil. Pink rot can affect tubers when they are in the field or if they are injured during harvest.

The fungus sickness has recently been a problem for several Manitoba producers, according to the business. These issues prompted Simplot to highlight the virus in an August communication to producers this year.

“Once they’ve dug it and they’ve put it in the pile with their healthy potatoes, they’re in trouble. The biggest thing is to avoid harvesting and mixing rot areas of the field with healthy areas of the field,” Graham added.

In terms of the pathogen, spoilage is the biggest issue. Producers will see a dark brownish-gray discoloration on infected potatoes from the exterior, which is simple to confuse with late blight. The most alarming symptom, though, appears after slicing. The disease gets its name from the fact that when a potato is exposed to air, the interior develops a pink tint.

This first color change happens around 20 minutes after cutting, according to the Ontario Ministry of Agriculture, Food, and Rural Affairs. The hue becomes significantly less appealing after an hour. The flesh of the tubers darkens from white to gray, then to brown (or even black, depending on the extension material).

The same Ontario department warns that post-storage spread can occur ‘when liquid oozes from rotting tubers’ creating favorable conditions for soft rot.

“Infected tubers should be graded out to avoid poor crop emergence in the spring and storage losses. Monitor storages closely to determine the development of hot spots,” government materials suggest.

Replying to questions addressed by the Manitoba Co-operator, Vikram Bisht, Manitoba Agriculture potato and horticulture crop pathologist, added: “Often the infected tubers will have secondary rot in storage and are often graded out and so not used as seed. However, in storage, the spores on infected tubers could contaminate other tubers and become a source of inoculum.”

Even without pink rot infection, some potato cultivars may naturally become pink after slicing, according to a Simplot newsletter.