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Glyphosate is one of the most widely used herbicides in the North America. The widespread use of glyphosate is due in part to its very broad weed spectrum and high efficacy.
Additionally, glyphosate-resistant crops allow in-crop use of the herbicide without the risk of crop injury.
- Glyphosate must contact and be retained on a weed canopy and diffuse through four absorption barriers before being translocated to its subcellular target site.
- Environmental conditions, such as extremes in temperature, soil moisture, wind speed and humidity can enhance or reduce glyphosate absorption and translocation. Long- or short-term droughty conditions most often reduce field performance.
- Although considered a non-selective herbicide, some weed species have an inherently high tolerance to glyphosate. Morningglory species and wild buckwheat are among the most tolerant.
- Ammonium sulfate and a non-ionic surfactant contribute to glyphosate absorption and efficacy; many products include a non-ionic surfactant, however, so carefully consult the appropriate label.
- Only the glyphosate parent acid has herbicidal activity, so acid equivalent (a.e.) concentration should be used for product rate calculation.
- The standard rate of glyphosate is 0.75 lb. a.e. per acre. The rate should be increased to 1.13 for weed height ranging from 6 to 12 inches and to 1.50 for weeds > 12 inches tall.
- To maximize crop yield, glyphosate should be applied to weeds < 4 inches tall in corn, and weeds < 6 inches tall in soybean. Timing optima however can vary with weather, weed populations and cropping management practices.
- Pre-emerge herbicides followed by foliar glyphosate can increase crop yield and reduce the in-crop timing sensitivity of glyphosate.
Additionally, glyphosate-resistant crops allow in-crop use of the herbicide without the risk of crop injury. This Crop Insights by Jeff Wessel discusses glyphosate use practices to optimize weed control and crop yield.