Glyphosate resistance self-inflicted?
A recent
Delta Farm Press article in talks about increasing failures with barnyardgrass in places like Minnesota and Arkansas. Barnyardgrass is one of the few grass weed species that growers have had to face failing with glyphosate. All the more reason to look for alternative management practices to keep things on an even keel.
LibertyLink® soybeans are on the horizon and growers are looking at this as an alternative option to control weeds breaking through glyphosate. Growers are questioning if the earlier timing of application required for this technology in comparison to glyphosate-tolerant soybeans will be a disadvantage. The most interesting part of this question assumes that timing for glyphosate-tolerant soybean applications has changed or been delayed since their introduction. Not so. The label still states the "first glyphosate application at 10 to 14 days after soybean and weed emergence followed by a second application seven to 14 days later."
The introduction of glyphosate-tolerant soybeans brought about several benefits - economical, environmental, efficiency, ease of use, time saving, etc. But, have all the benefits of this outstanding technology allowed growers to become lax on proper management practices? Even if you aren't basing your application off timing, it is closely tied to the height of weeds at time of application. If you were to survey a group of neighbors to see at what weed height does the first application of glyphosate generally get applied, what would you find out?
Many university researchers have demonstrated what the ideal weed height should be at time of application in order to minimize weed competition and to optimize control. The picture below shows a waterhemp plant far beyond the ideal four to six inches at the time of application. How closely do you follow label recommendations for difficult to control weeds? How common is this scene to you? 
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