Resistant weeds, the appropriate use of herbicides and integrated weed management strategies are highlighted topics in the new white paper, “Overlapping Residual Herbicides” by Purdue University Associate Professor of Weed Science Bryan Young, pictured here talking weed control strategies at the 2014 Commodity Classic.

“The practice of applying two effective residual herbicide sites of action in combination or the concept of using effective residual herbicides in sequential overlapping applications would both be considered a best management practice to deter the development of herbicide-resistant weeds,” writes Young.

The white paper includes research related to glyphosate-resistance in reference to the three most problematic weeds confronting farmers in the major corn and soybean production areas of the United States: waterhemp, Palmer amaranth and horseweed (or marestail). These aggressive weed species can reduce soybean yields by 40 percent or more and have become problematic for growers due to prolific seed production, continuous weed emergence throughout the growing season, ease of seed dispersal and ease of overcoming or escaping herbicide-based management tactics. Soil applied residual herbicides are the most frequently recommended because of the multiple benefits, which are further explored in the white paper.

“The most common approach to managing herbicide-resistant weed species such as glyphosate-resistant horseweed, Palmer amaranth or waterhemp has been the use of an effective alternative herbicide as a tank-mixture with glyphosate as a residual herbicide preceding a postemergence application of glyphosate, or a combination of both,” writes Young.

FMC Corporation has been promoting the overlap system this year to farmers as a way to control weed resistance.