Smooth pigweed (Amaranthus hybridus) control from atrazine and/or simazine (Princep) has been unsatisfactory in some Kentucky corn fields. Many of these fields have grown corn where one or both of these herbicides have been used continuously for several years. These two triazine herbicides, particularly atrazine, are used annually on over 90% of the corn grown in Kentucky. Other areas in the U.S. and around the world have reported. unsatisfactory control from atrazine where triazine resistant pigweed has developed.
Green, Jonathan D.; Barett, Michael; and Radford, Mike, "Triazine Resistant Pigweeds in Kentucky Corn Fields" (1990). Agronomy Notes. 98.