May 25, 2007

The proliferation of glyphosate-based products in recent years is unprecedented. Currently, there are more than 40 glyphosate-based herbicides registered for use in Nebraska, which has led to increased competition among products and generally lower product prices.

Given the number of products available, we compared efficacy of a variety of glyphosate-based products (generic and brand names) on weed control over three years at six locations in Nebraska. Weed species included: velvetleaf, common waterhemp, sunflower, kochia, Russian thistle, lambsquarters and a mix of foxtail species. Depending on the year or location, we tested these glyphosate-based products at two rates (label rate and half-rate): Roundup Ultra®, Roundup UltraDRY®, Roundup UltraMAX®, Roundup WeatherMAX®, Touchdown w/IQ®, Cornerstone®, Clearout 41 Plus®, GlyphoMAX®, Glyfos Xtra® and Glyphomax Plus®.

All herbicides provided excellent weed control (> 90%) regardless of the rate or brand name. For example, there was no significant difference in the level of weed control for Roundup Ultra Dry and the generic Clearout41 Plus. The level of weed control was not significantly different for Roundup WeatherMax and the generic product Clearout41 Plus, or any other herbicide tested.

These findings are similar to those reported by researchers in other states. Generic glyphosate-based products can provide a valuable tool for weed control in glyphosate-tolerant crops as well as allow for reduced weed control costs. Producers can select the appropriate herbicide rate for the weeds present, environmental factors, and herbicide costs, rather than choosing a glyphosate trade name.

In addition, with the growing popularity of the relatively inexpensive generic glyphosate- based products, there is an even greater need for their proper use. Their value can be preserved only by proper management. This will become even more important as other Roundup-Ready crops become available (e.g. Roundup-Ready corn and Roundup-Ready alfalfa). When one Roundup-Ready crop is grown after another, it's easy to fall into a trap of overusing glyphosate.

Proper use of glyphosate-based technology, as a component of an integrated weed management program, is the key to preserving the long-term benefits of this technology while avoiding many of the concerns about its use, or misuse. For more information, see Use of Herbicide Tolerant Crops as a Component of an Integrated Weed Management Program.

Stevan Knezevic
Integrated Weed Management Specialist
Haskell Ag Lab, Concord