Northern U.S.–Adapted 2,4‐D‐Resistant Red Clover

2,4‐Dichlorophenoxyacetic acid (2,4‐D)–resistant red clover ( Trifolium pratense L.) varieties would offer producers more weed control options, particularly in mixed grass–red clover pastures. In the 1980s, work was initiated in Florida to select for 2,4‐D‐tolerant red clover. However, this Florida germplasm was not adapted to cool, humid regions in the northern United States. A greenhouse selection program was initiated to develop 2,4‐D‐resistant germplasm (WI‐2,4D12) that is more adapted to the northern United States. A study was conducted to determine field resistance of the WI‐2,4D12 germplasm to 2,4‐D application. Two months post‐2,4‐D application (1.3 kg a.i. ha −1 ) plant percentage survival rates of 84.3% of WI‐2,4D12 red clover compared with 7.7% of non‐herbicide‐tolerant standard red clover were observed. Postherbicide application WI‐2,4D12 red clover plant vigor ratings were 71.2% of their preherbicide application ratings, while postherbicide application non‐herbicide‐tolerant red clover plant vigor ratings were at 2.2% of their preherbicide application ratings. This study confirms the feasibility of developing herbicide‐resistant forage crops using conventional breeding. Future breeding work should focus on further improving red clover 2,4‐D tolerance to eliminate herbicide plant injury. Ascertaining the genetic basis of this resistance would facilitate more rapid movement of the resistance into commercial red clover cultivars.