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A Weeds Management Strategy may or may not Include Soil-Applied Herbicides (05/05/16)

A survey of weed control and production practices in sugarbeet has been compiled annually since 1968.

A Weeds Management Strategy may or may not Include Soil-Applied Herbicides

A survey of weed control and production practices in sugarbeet has been compiled annually since 1968. The 2015 survey indicated that soil-applied herbicides were used on 60% of the sugarbeet acreage or a 41% increase from results reported in the 2014 survey. Similar survey questions were used during winter sugarbeet grower meetings in Willmar, MN, Wahpeton, ND and Grand Forks, ND. Survey results indicated a very strong geographic bias with respect to soil-applied herbicide use. That is, respondents indicated soil-applied herbicides (PPI, PRE or early postemergence) were used on 109% and 124% of the sugarbeet acreage, respectively, among growers attending the Wahpeton and Willmar meetings. Fourteen percent of respondents attending the Grand Forks meeting reported soil-applied herbicide use.

Sugarbeet growers in southern Minnesota, west central Minnesota and the southern area of the Red River Valley use soil applied herbicides for control of waterhemp, a pigweed species that is frequently found in fields and a weed species that has developed tolerance to glyphosate. These producers have changed their weed control practices in response to a very important weed threat. However, we learned use of soil-applied herbicides is not widespread. Over 60% of sugarbeet growers in the central and northern areas of the Red River Valley reported one or two glyphosate applications over RR sugarbeet and greater than 90% indicated excellent or good results.

Pick-up any farm magazine this past winter and you certainly found an article about weed resistance; the authors frequently advocating soil applied herbicides as a resistance management solution. I don’t completely agree. I believe the leap from perhaps using multiple applications of a single herbicide to soil-applied herbicides is too great. I also believe a one-size-fits-all approach is too simplistic and doesn’t represent reality.

We need to return to use of strong agronomic principles with respect to weeds management. Principles including scouting fields, identifying weeds and making detailed maps indicating where weeds occur in fields. And working with your agriculturalist to prioritize the weed and herbicides that on your farm will require a proactive weeds management strategy. For example, weeds that if not controlled, have a greater impact on crop yield. Or a weed that may have fewer options for its control across the sequence. Develop mixes with two or three effective herbicides from planting through harvest. And all the better if your strategy includes soil-applied herbicides. Create an expectation for zero tolerance for weed escapes in fields, even if it means pulling weeds by hand. Pay special attention to the boundaries of fields and even ditches. Yes, we may increase herbicide use. Finally, the weeds management strategy is not a single program approach that can be replicated across farms, townships or counties. Problematic weeds and resultant solutions may differ even from township-to-township so the solution on one farm might be different from the solution on the next farm.

Tom Peters

 Extension Sugarbeet Agronomist

NDSU & U of MN

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