EROME, Idaho—Amalgamated Sugar officials say 2015 has produced a record sugarbeet crop, despite pressure from two diseases that hadn’t been a problem for growers in the past.
With a small percentage of the crop remaining to be harvested, Rupert grower Duane Grant, chairman of Snake River Sugar Co., said the company estimates growers produced a record 38 tons per acre, up from 37.35 tons per acre last season.
Grant said the percentage of sugar was also be up, averaging nearly 17.4 percent, compared with last season’s levels of 17.25 percent.
Grant said sugar content has dropped somewhat in the late-harvested crops, with recent moisture bulking beets and diluting sugars.
Oliver Neher, an Amalgamated pathologist, said a warm and moist growing season enabled two diseases Idaho beet growers don’t normally battle to flare up.
“It’s high nighttime temperatures that hurt us, in combination with humidity,” Neher said, advising growers to stagger which beet fields they irrigate during the night.
The fungal disease Cercospora leaf spot has long plagued growers in Michigan and the Red River Valley of Minnesota and North Dakota, significantly reducing sugar content, yields and storage life. Neher said Idaho growers often see small pockets of Cercospora, but this season, fields in the Minidoka area were heavily infested, and he suspects infections were widespread throughout Magic Valley.
Complicating matters, Neher said, many Idaho growers used Inspire XT and Eminent in their fungicide programs to control powdery mildew, and Cercospora is resistant to both chemicals. Furthermore, powdery mildew is resistant to Headline and Gem, two of the best chemistries for controlling Cercospora.
Neher said spraying for Cercospora wasn’t necessary in the past, but this season, some fields would have benefited from one or two applications.
Neher sees little potential at the moment for planting Cercospora-resistant varieties, as other diseases, such as curly top, are still more economically important. But he advises growers to pay close attention for the tell-tale reddish-brown lesions with light-brown centers and purple margins when scouting fields.
Another new disease to the area could affect beet growers who follow potatoes in their rotations.
At the University of Idaho’s Parma Research and Extension Center and in Washington fields, the fungus responsible for black dot disease in potatoes, Colletotrichum coccodes, has infected the subsequent crop of sugarbeets, Neher said. Neher said the problem first surfaced in 2014.
“We do not have any idea yet what it will do to our sugarbeets,” Neher said. “If (the fungus) can grow and multiply on sugarbeets that might put additional pressure on potato growers if they have beets and potatoes in the same rotation.”
Grant’s agronomist, Alan Mohlman, plans to watch the black dot issue closely, as he plants beets following potatoes about 80 percent of the time.
Mohlman suspects Idaho’s yield records would have been even greater, if not for Cercospora. He said he chose fungicides that are no longer effective against the disease, and he anticipates treating more for Cercospora in the future.
“This year, it totally took the canopy down,” Mohlman said. “We just got caught with our pants down, basically.“
Source: www.capitalpress.com