Absorption, Translocation, and Phytotoxicity of Glyphosate in Bulbous Oatgrass (Arrhenatherum elatius var. bulbosum)

Efficacy of glyphosate on bulbous oatgrass, a creeping perennial grass, was investigated in greenhouse and growth chamber studies. Glyphosate at 1.2 and 2.5 kg ae ha−1 significantly reduced corm formation and corm viability. Glyphosate controlled bulbous oatgrass when applied at the 4- to 5- or 6- to 7-leaf stage. With 2.5 kg ha−1, a 24-h period between glyphosate application and removal of the shoots was sufficient to cause maximum reduction in regrowth. Total amount of 14C translocated out of leaves treated with radiolabeled glyphosate (1.0 kg ha−1 total glyphosate) did not differ among growth stages, but more 14C accumulated in the dormant corms when glyphosate was applied at the 2- to 3-leaf stage than at the 4- to 5- or 6- to 7-leaf stages. Lack of correlation between maximum plant injury and glyphosate accumulation in corms is not understood but may be related to differences in application method in the two studies.