Soybean Burndown Options When 2,4-D Cannot Be Used

April 23, 2009 at 7:30 am

Unfortunately, the weather has not been the most cooperative this spring for fieldwork.  Cool, wet conditions are delaying field work and as we get closer to May many growers may drop 2,4-D from their soybean burndown.  Dr. Mark Loux, OSU Weed Specialist, suggests that where it’s not possible to use 2,4-D in a soybean burndown consider applying a combination of glyphosate plus products such as Canopy EX or DF, Valor XLT, or Envive. The addition of one of those products to glyphosate in a soybean burndown will provide generally broad-spectrum control of no-till weeds in the absence of 2,4-D. In addition, adding one of those products to glyphosate will help on the tough to control dandelion. But there are other products that will work well too. Mixtures of glyphosate with Gangster or Sonic/Authority First, are also more broad-spectrum than glyphosate alone. Actually, these products can be more effective for control of emerged ragweeds and marestail (as long as they are not ALS-resistant), but overall Gangster or Sonic/Authority First are less effective on a number of winter annual weeds including dandelion.

In addition to adding one of those soybean residual herbicides mentioned above to glyphosate, Dr. Loux recommends increasing the glyphosate rate from 0.75 lbs ae/A (22 – 24 oz of newer glyphosate formulations and 32 oz of generic glyphosate formulations) to 1.1 or 1.5 lbs acid equivalent per acre.  This increased glyphosate rate will help improve control in mixtures with soybean residual herbicides. But keep in mind that even mixtures of high rates of glyphosate and ALS-based soybean residual herbicides will not control populations of marestail or ragweeds that have developed resistance to both glyphosate and ALS inhibitors. In summary, for growers that cannot use 2,4-D in a soybean burndown OSU strongly recommends using one of the residual soybean herbicides mentioned here plus glyphosate at a rate of at least 1.5 lb acid equivalent per acre.

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