Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2012
Publication Date: 7/1/2012
Citation: Bukun, B., Nissen, S., Shaner, D.L. 2012. Imazamox Absorption, Translocation and Metabolism in Red Lentil (Lens culinaris Medic.) and Dry Bean (Phaseolus vulgaris L.). Weed Science. Interpretive Summary: Lentils are a valuable crop for many dryland situations. Weeds compete vigorously with lentils, causing major yield losses. Weed management is a problem in lentils due to the lack of selective herbicides. Imazamox is a widely used herbicide to control weeds in many leguminous crops. However, it cannot be used in lentils due to unacceptable injury. The goal of this work was to determine the reason why lentils are damaged by imazamox, while dry beans, another edible legume, can tolerate the herbicide. We found that lentils cannot rapidly metabolize imazamox to non-toxic forms whereas dry beans can. These results suggest that the sensitivity of lentils to imazamox is inherent and there is little that can be done to increase selectivity.
Technical Abstract: Imazamox is an imidazolinone herbicide used to control many grasses and broadleaf weeds in leguminous crops such as soybeans, alfalfa and dry beans; however, imazamox cannot be used on red lentils because of unacceptable injury. Studies were conducted to compare imazamox absorption, translocation and metabolism in red lentil and dry bean to determine if any or all of these factors contributed to differential crop sensitivity. Radiolabeled imazamox was applied to three young red lentil leaves and to a fully expanded dry bean trifoliate. By 96 h after treatment (HAT), red lentil leaves absorbed more 14C-imazamox than dry bean, 78.8% and 62.8%, respectively.. Imazamox was also absorbed more rapidly by lentil, (72.6% and 54% of applied dose by12 HAT, in lentils and dry beans, respectively). 14C-imazamox translocation out of the treated leaf was significantly higher in red lentils compared to dry bean, (15.7% and 0.55% of the applied dose, respectively at 96 HAT). Translocation of 14C-imazamox was greater to red lentil roots compared to the shoot (9.1% and 6.6% of the applied dose, respectively, at 96 HAT.) Less than 1% of 14C-imazamox translocated out of the treated leaf to the roots and shoots in dry bean. The half life of 14C-imazamox in dry beans was less than 6 h, whereas it was greater than 96 h in red lentils, although both species metabolized the herbicide to more polar metabolites. This difference in the rate of metabolism of imazamox between the two crops is the primary reason for the greater selectivity of imazamox on dry beans compared to red lentils.