The site, http://www.weedtool.com, asks a series of ten questions for producer response, said Bernards. Based on those responses, a Risk Rating Score will be charted from lowest to greatest risk of developing glyphosate resistance. The producer then reviews the three highest priority areas and the associated "best farming practices" to lower weed resistance risk.
Several universities’ weed science programs maintain additional Websites that provide more information about effective weed management practices, Bernards said.
“Marestail” or horseweed, has shown some resistance in several eastern Nebraska counties. This weed has a light, wind-blown seed and it spreads very rapidly.
“Marestail has only been confirmed resistant to glyphosate in Saunders County, but it would not be prudent to rely solely on glyphosate to control it anywhere it grows in Nebraska,” Bernards said.
The best ways to prevent herbicide resistance are to use a combination of herbicides, cultivation, and crop rotation to manage weeds, and where possible not to use glyphosate every year, Bernards said.
But since most soybeans and corn grown in Nebraska are Roundup® Ready, glyphosate is used on most acres every year. To minimize risk of developing resistance to glyphosate, effective strategies include using a residual herbicide before planting the crop to control some of the weeds, or if a pre-emergent herbicide isn’t an option, mixing another post-emergence herbicide with glyphosate.
Besides Weed Tool, Bernards said that http://www.glyphosateweedscrops.org provides a series of brochures on controlling glyphosate resistance risk, as well as articles and links.
Managing glyphosate resistance will help keep this valuable herbicide viable for future crops.
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