Glyphosate Resistant Giant Ragweed Control in Cotton

Giant ragweed is becoming a more prevalent problem in cotton fields in Tennessee.  Historically, giant ragweed was mostly confined to field edges but in recent years has progressively spread into cotton fields.  In just the last two years growers reported that glyphosate was not providing the same level of giant ragweed control as before.  Field as well as greenhouse research has shown that giant ragweed in our cotton fields has more tolerance to glyphosate than giant ragweed in fence rows.  Research was conducted in 2009 looking at post control options in Phytogen Widestrike cotton.  Results of this research will be presented.