2020 INTERNSPublished May 20, 2020
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Glyphosate- or multiple-resistant horseweed, or
Because of resistance problems and weather conditions that favored horseweed emergence in 2014, horseweed control failures in soybeans were by far the most common phone call I received last summer. Many of these control failures could have been avoided with an appropriate burndown herbicide program. To control horseweed, whether it is glyphosate-resistant, ALS-resistant or contains multiple resistances to both classes of herbicides, it is extremely important to take a proactive approach.
Effective burndown options for horseweed control
To effectively manage horseweed, it is important to control horseweed prior to planting. 2,4-D ester (1 pint per acre) or Sharpen (1 fluid ounce per acre) should be included in glyphosate burndown applications prior to planting soybeans. Remember a minimum of seven days is needed between the application of 2,4-D ester (1 pint per acre) and soybean planting. Methylated seed oil at 1 percent v/v must be included with Sharpen plus glyphosate
Liberty (29-36 fluid ounces per acre) plus Sharpen (1 fluid ounce per acre) plus MSO (1 percent v/v) plus AMS, or Gramoxone (3 points) plus Metribuzin (8 fluid ounces) plus crop oil concentrate (1 percent v/v) are two other burndown treatments that were extremely effective at controlling glyphosate-resistant horseweed.
Horseweed is most susceptible in the rosette stage (less than 2 inches in height). Herbicides should be applied before plants are 4-6 inches in height. Spring burndown applications with residuals will help prevent
In soybeans, the herbicides that provide
Remember, many of these products have pH restrictions and long rotation restrictions to
For more information and specific herbicide recommendations, see the Controlling Horseweed (Marestail) fact sheet on page 189 in “2015 Weed Control Guide for Field Crops,” Michigan State University Extension Bulletin E-434. Also, visit TakeActionOnWeeds.com to view a regional bulletin on the “Management of Herbicide-Resistant Horseweed in No-till Soybeans.”
Source: Christy Sprague, Michigan State University Extension
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