Abstract: Differential response of wild carrot to 2,4-D was found in seeds collected from 10 locations in Michigan, three in Ohio, one in Illinois, and one in Ontario, Canada. Greenhouse studies were conducted on plants grown from the collected seeds to confirm resistance of wild carrot to 2,4-D, and to study variations among and within populations. The differential response of wild carrot to 2,4-D in field research was due to resistant individuals. Among the 14 locations, wild carrot control with 2,4-D ranged from 18 to 91%. Wild carrot varied in its response to 2,4-D among and within populations as well as within individual umbels. In 69% of the tested samples, at least one wild carrot plant was resistant to 2,4-D.
Nomenclature: 2,4-D, (2,4-dichlorophenoxy) acetic acid; wild carrot, Daucus carota L. #3 DAUCA.
Additional index words: Herbicide resistance, differential response, growth regulator.
Abbreviations: DAT, days after treatment.
