Fall Herbicide Treatments for Next Year’s No-Till

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Fall herbicide treatments have been discussed as options for no-till crops. The idea is to apply an herbicide this fall that will control existing weeds and possibly provide residual weed control so that fields do not have lots of vegetation next spring. Less vegetation in the spring allows the soil to warm up faster and conserve moisture. This practice has worked in many of the Midwest states, but their winters are colder and often with more snow cover. We have looked at various herbicides the past few years for no-till soybeans. Products tested include Valor, Canopy EX, and Express. In our trials the fall treatments were applied with 2,4-D plus Gramoxone or glyphosate. Applications were made in late October to mid-November, after weeds have emerged. Most of the products provided some control when evaluated in March. The remaining weeds were small and less vigorous. However, as the spring progressed Valor and Express became much less effective, as well as allowed for spring germination of many species. Those plants that were present were large by early May. As a result, non-selective herbicide was needed before soybean planting. However, fall treatments helped to conserve spring moisture and provided for a better soybean stand when rainfall was limited. In 2006 and 2007, Canopy EX applied in the fall with Gramoxone or glyphosate provided excellent weed control up to the time of soybean planting (including horseweed). Canopy EX restricts your rotation to allow only soybeans the following spring.

Fall treatments should be applied while the plants are still actively growing. If you are considering a fall herbicide program, be sure to consider all pros and cons, including resistance management.

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