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Weed stampede: Beets, other crops should reset herbicides to May-planted crop

A single waterhemp plant produces hundreds of thousands of seeds. Plants that emerged early in 2015 were just beginning to shed seed in late August. Mikkel Pates / Forum News Service1 / 2
Tom Peters, extension sugar beet weed specialist based in Fargo, for the University of Minnesota and North Dakota State University, strongly urges sugar beet, corn and soybean producers to use pre-emergence herbicides to control waterhemp. Trevor Peterson / Forum News Service2 / 2

FARGO — With sugar beet planting likely delayed until early May because of snow and cold, Tom Peters says farmers should set their sites on using pre-emergence herbicides to control waterhemp, and focus on that as much as they do on getting seed in the ground.

"There's this idea that — especially in a late year — we have to put all of our energy on planting, that we have to get everything planted as quickly as possible," says Peters, Extension Service sugar beet weed specialist for both North Dakota State University and the University of Minnesota. "We're going to get into trouble if we get some rain events and start to see some weeds emerge."

Waterhemp is a pigweed that's moved into the Red River Valley from the south. It germinates a little later than lambsquarter, kochia and the more common redroot pigweed. It germinates and emerges about May 15 in a normal year in the southern Red River Valley and west central Minnesota.

Waterhemp plants are sometimes glyphosate-resistant and sometimes not. Each surviving plant can produce thousands of seed. Peters uses glyphosate for other weeds and for nonresistant waterhemp, but "you have to plan for the resistant population," he says.

Where waterhemp is "the primary concern," Peters wants farmers to consider "staging" their planting. Within reason, that means rather than planting everything and then going back and applying herbicides, the farmer plants a field, immediately applies pre-emergence weed control, then repeats elsewhere.

"I'm afraid that if we plant everything and then focus on the herbicide application later on, I'm afraid we'll get to the same place — caught in between where weeds start to germinate and emerge before we have activated product," Peters says.

Interviewed at his NDSU office on April 11, Peters noted that was the date farmers could plant sugar beets in North Dakota and be eligible for full crop insurance indemnities and the date many farmers had planted beets the year before.

"I will be surprised if we have many acres seeded at all during the month of April," he says.

Weeds won't wait

"Our strategy in sugar beet has been to allow the sugar beet to get to the two-leaf stage before we make our herbicide application," Peters says. If sugar beets were planted in the normal April 15 time frame, the two-leaf stage is about May 5 to May 10. That's not going to happen this year.

"Sugar beets aren't the right growth stage, but waterhemp is still going to germinate and emerge at the same time. Because of that, we have to change our plan."

"The bottom line is that farmers need to use a pre-emergence herbicide," Peters says. For beets there are three or four options to consider, ranging from products incorporated into the soil to products applied to the soil at planting time and activated by rain.

Peters says 35 percent of growers attending sugar beet grower seminars in January and February said waterhemp is "their most important production challenge. It keeps creeping up," both in percentage and distance north, Peters says. "I get a lot of questions in the Grand Forks, N.D., and Crookston, Minn., area."

Waterhemp bedevils every acre in Southern Minnesota Beet Sugar Cooperative country at Renville, Minn., and every acre at Minn-Dak Farmers Cooperative in Wahpeton, N.D. It's also in an area from Ada, Minn., to Hillsboro, N.D., and southward in the American Crystal Sugar Co., area of Moorhead, Minn.

"One hundred percent of the farmers are using this concept we call 'lay-by,' where they apply a soil-applied herbicide that is post-emergence to sugar beet and pre-emergence to waterhemp" weeds, Peters says. Roughly half of the sugar beet farmers in waterhemp areas use a pre-emergent herbicide — applied immediately after planting, before the beets emerge.

Dicamba issue

It doesn't matter if a farmer is growing sugar beets, soybeans or corn, Peters says:

"Waterhemp doesn't care. It's going to germinate at the same time. The mindset for the corn grower is, 'I'm going to use a pre-emergence herbicide.' The mindset for the soybean grower is a combination of both. Some see the value of pre-emergence herbicides. I would guess the majority do not and don't use a pre-emergence product at all."

He says the introduction of dicamba-tolerant soybean seeds created an impression that post-emergent weed control would continue to be viable. However, Peters says the pre-emergence program is actually more consistently reliable.

Peters would argue that farmers need to use a pre-emergence herbicide in soybeans as well in 2018 because of the late spring.

"The same logic that applies to sugar beets applies to soybeans as well," he says.