HERBICIDE EFFECT ON THE VIABILITY OF QUACKGRASS (Agropyron repens) RHIZOME BUDS

Sethoxydim, glyphosate, haloxyfop-methyl, NCI 96683, fluazifop-butyl and RO 13-8895 were evaluated under controlled environment conditions for their ability to translocate from treated quackgrass shoots to rhizome nodal buds. Two techniques to evaluate rhizome bud viability were utilized. In general, more rhizome buds showed signs of respiratory activity as evaluated by the tetrazolium chloride assay than did those which showed evidence of bud growth when single buds were grown in an agar medium. Both bioassays indicated all the herbicides tested were more effective against younger (three leaf) plants than older (five leaf) plants. None of the herbicides tested completely eliminated either bud viability or the formation of new rhizome buds subsequent to treatment. The least effective herbicide tested was RO 13-8895. The most effective compounds were sethoxydim and haloxyfop-methyl. Glyphosate and fluazifop-butyl were of intermediate efficacy while NCI 96683 efficacy was between those two groups depending on the part of the rhizome being considered.Key words: Tetrazolium chloride, translocation, glyphosate, sethoxydim, haloxyfop-methyl, fluazifop-butyl