A comparison of dicamba absorption, translocation and metabolism in Chenopodium album populations resistant and susceptible to dicamba

Chenopodium album is a troublesome arable weed species which has evolved resistance to dicamba in New Zealand. The objective of this work was to investigate the patterns of absorption, translocation and metabolism of dicamba in resistant and susceptible C. album populations. No significant differences in absorption by the two populations were measured, with over 80% of applied herbicide entering the plants of both populations during the 5 days after application. The 14C from dicamba was also readily translocated out of the treated leaf, with this occurring more rapidly in resistant plants than susceptible plants. The majority of the 14C from dicamba was translocated into untreated leaves in both populations. However, by 5 days after application, 18.4% of the absorbed 14C from dicamba was found in stem material for susceptible plants, compared with only 5.1% for resistant plants. No dicamba metabolism was detected for either population. Based on the results of this study, the mechanism of resistance to dicamba in C. album could not be adequately explained by differential patterns of absorption, translocation or metabolism, but the mechanism appears to differ from previously published cases of dicamba resistance.