Recent greenhouse testing confirms an increase in the number of North Dakota and Minnesota fields with glyphosate resistant common and giant ragweed, says Jeff Stachler, NDSU Extension weed specialist.

In northwest Minnesota, glyphosate resistant common ragweed was recently confirmed in Pennington County.

Since the 2008 and 2009 growing seasons, glyphosate-resistant common ragweed has been confirmed in a total of four fields in Clay County (Hawley to Hitterdal area), Minn., three fields in Cass County (Casselton to Kindred area), N.D., two fields in Red Lake County (Plummer area), Minn.; and Traill County  (Buxton area), N.D.; and one field in Pennington, Stearns and Todd Counties, Minn.

In Minnesota, glyphosate resistant giant ragweed was recently confirmed in Renville and Sibley Counties. Since 2006, glyphosate-resistant giant ragweed has been confirmed in 15 fields in the following counties: Meeker, McLeod, Renville, Sibley, and Yellow Medicine. The greatest concentration (11 fields) of glyphosate-resistant giant ragweed can be found in McLeod County and eastern Renville County. It is likely that 60 to 95% of all fields in this area have some frequency of glyphosate resistant giant ragweed.

Based upon recent greenhouse testing by Michael Moechnig at South Dakota State University, glyphosate resistant kochia is likely present in south central North Dakota.

Source: NDSU Crop Pest Report