Effects of Phenology on Translocation Patterns of Several Herbicides in Quackgrass,Agropyron repens

Abstract

A growth room study was conducted to evaluate the effect that timing of application has on the distribution of several herbicides in quackgrass. Uniformly labeled14C-sucrose and the radiolabeled herbicides glyphosate, sethoxydim, the butyl ester of fluazifop, and the methyl ester of haloxyfop were applied to quackgrass (ranging from the three- to eight-leaf stage) propagated from six-bud rhizome segments. Five days after treatment the plants were harvested, lyophilized, and later sectioned, mapped, and oxidized in preparation for14C quantification. In most cases, slightly more14C was translocated to the shoots than to the rhizomes.14C translocation to the rhizomes was similar at all growth stages. The14C accumulating in the rhizomes exhibited a nonuniform distribution pattern with more14C in the distal areas of new rhizomes than in the other areas of the rhizome system. Plants treated with haloxyfop had a more uniform distribution of14C along their rhizomes than did those treated with fluazifop or sethoxydim.