Resistant ragweed

Jan 31, 2005 12:40 PM

Glyphosate-resistant ragweed found in Missouri

Monsanto recently announced that a common ragweed in one field in central Missouri is resistant to glyposate. Monsanto reported that the resistant determination was made jointly by the company and University of Missouri weed scientist Reid Smeda. The resistant ragweed was confined to a 20-acre section of the field, according to the Monsanto news release. Common ragweed now joins some biotypes of marestail and ryegrass shown to be resistant to glyphosate. Monsanto points out that these resistant cases are managed with tank mixes, which is the suggested treatment for common ragweed. The company recommends tank mixing FlexStar or Phoenix herbicides with Roundup for post-emergence applictions in soybeans to treat resistant ragweed. Another option is Valor or Scepter for soil applied programs. In corn, herbicides such as triazines and growth regulators may be added to the herbicide program.