ABSORPTION, TRANSLOCATION, AND ACTIVITY OF CGA-136872, DPX-V9360, AND GLYPHOSATE IN RHIZOME JOHNSONGRASS (SORGHUM-HALEPENSE)

Rhizome johnsongrass grown in the greenhouse and treated with glyphosate at 1680 g ai ha-1 at an early (3- to 4-leaf) or late (6- to 8-leaf) growth stage displayed injury within a week. Plants treated with CGA-136872 or DPX-V9360 at 40 g ai ha-1 at both growth stages displayed injury 1 to 2 weeks later. CGA-136872 did not prevent regrowth at either growth stage. No regrowth occurred from DPX-V9360 or glyphosate-treated plants. Foliar absorption by greenhouse-grown plants within 24 h of application was greater with C-14-glyphosate than with C-14-DPX-V9360 or C-14-CGA-136872. More C-14-DPX-V9360 was absorbed than C-14-CGA-136872. Growth stage influenced glyphosate absorption (more by younger plants) but not CGA-136872 or DPX-V9360 absorption. Translocation of the C-14-CGA-136872 and C-14-DPX-V9360 out of the treated leaf was less than 20% of the absorbed label and was less than glyphosate translocation. Growth stage of rhizome johnsongrass at the time of treatment had no effect on the distribution of radiolabeled herbicides within 24 h.