Home News Michigan Ag News Summer Disease, Insect Pressure in Michigan Potatoes

Summer Disease, Insect Pressure in Michigan Potatoes

Potato field near Three Rivers, Mich. Photo: Ashley Davenport
Potato field near Three Rivers, Mich. Photo: Ashley Davenport

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Parts of Michigan received a little relief from the heat last week with rain showers and cooler temperatures, but hot, dry conditions are back. How are Michigan’s potatoes handling the heat?

Some of that heat stress is alleviated by irrigation. However, Dr. Jamie Willbur, MSU assistant professor of integrated disease management in potato and sugarbeet production, said vascular diseases that started earlier in the season and age would be expressed in these conditions.

“They’re really working on bulking and growing the size of the tubers, and a lot of those resources from the leaves are going into the tubers underground,” she said. “That causes other natural senescence to happen up in the foliar canopy.”

She said that can lead to other diseases colonizing the lower leaves such as botrytis and early blight, particularly in irrigated fields.

“Those typically do colonize a lower canopy, especially as it’s under stress or starting to weaken with natural aging,” said Willbur.

Cases of those fungi aren’t any higher or lower than in previous years. Willbur said researchers aren’t seeing any potato white mold, which is atypical for this time of year. In irrigated fields, it may still be a concern to some growers.

“This fungus forms little mushrooms underneath the canopy right on the soil surface,” she said. “Those mushrooms require a cool, moist environment under a mostly closed, dense canopy. In previous years, we would have been starting to see some of this. With the heat, it’s been delayed this year.”

While managing disease pressure is important, Willbur added that at this time of the season, insects are more concerning.

“From what my sources and contacts in the field have shared with me, we had an abnormally significant amount of volunteer potatoes in the fields, and those volunteer potatoes promoted Colorado potato beetle overwintering,” said Willbur. “We have had abnormally high Colorado potato beetle pressure this year.”

For more information on MSU’s potato and sugarbeet pathology program, click here.