Late blight was found in Churchill, Mont., potato fields late last week, but agricultural experts and farmers said they are optimistic the disease would not have long-term affects on the seed potato industry in Montana’s Gallatin Valley.
Late blight is a “very serious disease” caused by an airborne pathogen that causes the potato to rot during storage if left untreated, according to Nina Zidack, director of the Montana State University Seed Potato Certification Program. Typically, late blight is first detected in the leaves of the plant as dark, water-soaked spots that eventually grow larger and become rough, dark-brown areas.
Zidack said the disease was found in potato fields Friday, Aug. 21 during a routine certification inspection. State representatives regularly inspect local potato fields for certification purposes. The Churchill area is the largest seed production area in the state, supplying roughly half of the state’s certified seed potatoes.
The Gallatin Valley provides a natural isolation that usually protects the potato crop from many diseases. This is the first time late blight has been detected in the valley, Zidack said.
Zidack declined to name the farms that were affected, but local grower John Venhuizen said nearly every grower in Churchill showed small signs of the disease. Venhuizen is the state board member of the United Potato Growers of America.
Since the outbreak was so widespread and in such small pockets, both Zidack and Venhuizen said the pathogen likely arrived during a long rainstorm earlier this month. Large potato farms in southern Idaho are battling a severe late blight outbreak. The disease travels by air and thrives in moist conditions.
“We’re speculating it possibly could have come in on a rain cloud,” Zidack said. “From the point when it landed on the leaves, it would probably take seven to 10 days before you would really see much infection. We had an all-day and all-night rain on Aug. 8. So just counting back when we found this on Aug 21, it’s logical that might have been the infection period.”
Venhuizen agreed and said the footprint of the blight points to the rainstorm theory.
“There’s really no other way it would have shown up scattered across the whole area like it did,” he said. “Nearly every grower ... had a touch, but it wasn’t easy to see.”
There are several factors lining up that should aid in the containment of the disease, both Zidack and Venhuizen said.
Since blight was detected so early, growers can apply fungicides to corral the disease, Zidack said. The current hot and dry weather also hinders the disease from spreading.
At this time of year, growers kill the potato plant vines in preparation of harvest. The process is called desiccation and allows growers to better control the quality and yield of the crop. Without the vines and its leaves, the spores are removed from the picture.
Everyone in the area sprayed fungicide to deal with the matter, Venhuizen said.
“Late blight is a manageable thing, but it’s not managed cheaply,” Venhuizen said.
The extra spraying will likely tack on an additional $50 to $100 per acre, which will affect farmers’ bottom line, Venhuizen said.
Late blight can also be spread if infected potatoes are planted in the spring. It can also spread if unused potatoes should sprout, or volunteer potatoes appear next year. Winter usually takes care of those problems, but if the area experiences a mild winter, the disease could come around again, Venhuizen said.
“I feel very confident that we won’t have any repercussions of this thing whatsoever, but it will make managing cull potatoes and volunteer potatoes” very important, he said. “If we get a really light winter without a hard frost, then they are going to bear watching for sure.”
The issue isn’t confined to farmers, both Venhuizen and Zidack said. Blight can also appear in backyard gardens, affecting both tomatoes and potatoes. If left unchecked, gardens can affect the agricultural community.
Zidack offered the following instructions for gardeners: “Home gardeners and those with market gardens should scout their potatoes and tomatoes, and if they see late blight, the best thing they can do at this point of the season is harvest potatoes. Any infected foliage should be disposed of in plastic bags. Symptoms can appear on leaves as round, brown lesions, sometimes bordered by a light green halo, and infections can also invade the stem, ultimately infecting the tubers. In tomatoes, the fruit can be infected as well.”
Source: Belgrade News