Unusually warm temperatures this September have been a blessing for grain producers across Western Canada. But the hot weather has made life difficult for potato producers, said a potato disease expert with Manitoba Agriculture.
“Storage of warm tubers infected with late blight (or contaminated with late blight spores) is very risky and has the potential to develop into major storage rot problems,” wrote Tracy Shinners-Carnelley in the government’s daily spud report.
When potatoes go into storage, the pulp temperatures should be between 10 and 18 C. But days in the high 20s last week, combined with warm nights, meant that some producers were storing potatoes at high temperatures, Shinners-Carnelley said.
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“Last week when harvest was continuing … there were definitely (warm) tubers that were making their way into storage bins,” she said.
This is not ideal because heat is a catalyst for disease.
“The factors that affect disease development in the field (heat and temperature) are also the same factors that affect disease risk in storage,” she said. “The warmer the potato pulp temperature of the tuber going in there (to storage) means the more heat you have to bring out of that pile.”
Putting warm potatoes into storage is a particular concern this year in Manitoba, because late blight has been detected in four commercial potato fields across the province.
The most recent case was detected last week in the central growing region around Portage la Prairie. At this stage of crop development, the disease is especially threatening, Shinners-Carnelley said.
“At this time of year … in addition to getting foliar late blight, there’s also the risk of tubers becoming infected,” she noted. “We’re now looking at storage season and the last thing that growers want to do is to put late blight infected tubers into their storage bins.”
Manitoba Agriculture reminded producers last week to monitor pulp temperatures and to dig only in the morning, but Shinners-Carnelley acknowledged it’s difficult for growers to put their harvest on hold, given that frost could hit at any time.
In many cases, growers were doing just that.
“They were starting early in the morning … and when the temperatures were getting too warm, they were shutting down,” she said.
“And of course it’s a time of year when people start to worry about when the first frost will come … so that’s a very delicate balance.”
Potato producers in North Dakota, South Dakota and Minnesota have been facing the same hot temperatures and harvest challenges over the last two weeks, said Chuck Gunnerson, president of the Northern Plains Potato Growers Association.
“Our harvest times have been either during the night or early morning hours, then we’ve been shut down for the rest of the day,” he said, noting that producers in the region are still early in the harvest.
“A number of processing potatoes have been dug … but as far as the seed potatoes, the fresh reds and the chipping potatoes, we’re probably just getting started.”
The story is similar in Manitoba, where the harvest is also a couple of weeks behind.
“I’m thinking we’re solidly in 20 percent (done) and could be a little higher,” said Tom Gonsalves, business development specialist for potatoes with Manitoba Agriculture
But the good news, Gonsalves added, is that the hot temperatures in September probably benefited the late seeded crops, so yields could be higher than expected.
