May 17, 2001

Sugarbeet Weed Control Decisions

The average planting date for sugarbeets will be later in 2001 than it has been for the past few years. That may have an influence on weed control decisions.

"The average soil temperature at planting will be higher this year as compared to years when planting was considerably earlier," according to Alan Dexter, North Dakota State University and University of Minnesota sugarbeet weed specialist. "Warm soil temperatures along with good soil moisture will allow more rapid emergence of sugarbeets and weeds."

Weeds are more likely to emerge before the sugarbeets with the warmer soil temperatures according to Dexter. "Roundup is an excellent choice to control weeds that have emerged before the sugarbeets," says Dexter. "But be sure that the sugarbeets have not started to emerge prior to Roundup treatment. Use of pre-emergence Roundup may allow for a short delay in the first micro-rate herbicide treatment, depending on weed emergence after Roundup. Growers should be, at this stage, monitoring their fields on a daily basis."

Dexter says the first micro-rate treatment should be applied when the largest sugarbeet plants in the field are in the early two-leaf stage. With warm soils, this stage may come as early as 14 days after planting as compared to the average of 21 days.

Timing between micro-rate applications should not exceed 7 days and the interval should be 5 days with ideal growing conditions since the micro-rate is most effective on very small weeds.

Dexter says sugarbeet herbicides cause more crop injury with higher temperatures and wet soils. "Sugarbeet injury occurs most often when a period of wet, cool weather is followed by a sudden switch to hot and sunny conditions. Conventional rates of sugarbeet herbicides always should be applied starting in late afternoon or early evening to reduce the risk of sugarbeet injury."

The micro-rate is safer than conventional rates and normally can be applied any time during the day notes Dexter. However, even micro-rate should be applied starting in late afternoon when a sudden change from cool and wet to hot and sunny occurs.

More information on growing sugarbeets is available on the Web at http://www.ag.ndsu.nodak.edu/media/beets/sgrbeet.htm .

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Source: Alan Dexter, (701) 231-8131, adexter@ndsuext.nodak.edu
Editor: Rich Mattern, (701) 231-6136, Richard_Mattern@ndsu.nodak.edu

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