Leaves of greenhouse-grown honey mesquite [Prosopis juliflora (Swartz) DC var. glandulosa (Torr.) Cockerell # PRCJG] initially absorbed more triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} from application of the ester than the amine salt. After 24 h, however, honey mesquite had absorbed 66% of the applied ester formulation and 72% of the amine formulation. Triclopyr was rapidly transported from the treated leaf to other plant parts. Triclopyr concentrations recovered 4 h after treatment in the upper canopy, lower canopy, and roots averaged 0.12, 0.19, and 0.09 μg, respectively. Concentrations of triclopyr recovered after 24 h were not significantly different than after 4 h in the canopy. No ester from ester application was recovered in the canopy, other than that in the treated leaf. Triclopyr recovered from stems of honey mesquite in the field ranged from 0.16 to 0.72 μg/g in phloem and from 0.04 to 0.20 μg/g in xylem from a broadcast spray application of the butoxyethanol ester at 1.12 kg/ha. Concentrations of triclopyr were usually not significantly different in either the upper or lower stems whether sampled 3 or 30 days after treatment.

Several new herbicides have been registered for pasture weed control, but their effect on ‘Coastal’ bermudagrass dry matter (DM) yield has not been documented. The objective of this study was to determine the effect of clopyralid, fluroxypyr, imazapic, picloram, picloram + fluroxypyr, picloram + 2,4-D amine, triasulfuron + dicamba, triclopyr amine + clopyralid, triclopyr ester, triclopyr ester + fluroxypyr, trifloxysulfuron, 2,4-D amine + dicamba, and 2,4-D ester on Coastal bermudagrass yield. Total DM yields of Coastal bermudagrass were not reduced by 0.84 kg/ha clopyralid, 0.031 kg ai/ha triasulfuron + 0.44 kg ai/ha dicamba, 1.205 kg ai/kg 2,4-D amine + 0.42 kg/ha dicamba, and 2.31 kg/ha 2,4-D ester. Although 0.227 kg ai/ha picloram + 0.84 kg/ha 2,4-D amine, 0.945 kg ai/ha triclopyr amine + 0.315 kg ai/ha clopyralid, and 1.68 kg ai/ha triclopyr ester reduced Coastal bermudagrass DM yields in harvest 1, there was no cumulative loss in total production in either 2001 or 2002 with these herbicides compared with that of the nontreated control. Coastal bermudagrass total DM yields were reduced by 52% with 0.158 kg ai/ha imazapic when applied to dormant bermudagrass in 2001, and by 26% with 0.021 kg ai/ha trifloxysulfuron when applied to actively growing bermudagrass in 2001; however, neither herbicide reduced total cumulative yield in 2002. In 2001 and 2002, total DM yield was reduced by an average of 25% with 0.42 kg/ha fluroxypyr, by 45% with 0.105 kg/ha imazapic, by 57% with 0.158 kg/ha imazapic, by 65% with 0.21 kg/ha imazapic, by 25% with 0.56 kg/ha picloram, by 20% with 0.188 kg/ha picloram + 0.188 kg/ha fluroxypyr, and by 18% with 0.63 kg/ha triclopyr ester + 0.21 kg/ha fluroxypyr, when applied to actively growing Coastal bermudagrass.