Comparison of Efficacy and Detection of Clethodim and Glyphosate Applied with Dicamba and 2,4-D through Tank Mixture and Sequential Applications

Greenhouse studies were planted at the R.R. Foil Plant Science Research Center in Starkville, MS. In the efficacy trial, pots were seeded with barnyardgrass ( ), broadleaf signalgrass ( ), and giant foxtail ( ). In the lab detection trial, only barnyardgrass was seeded. Both studies consisted of 16 treatments with four replications per treatment. The treatments consisted of clethodim, glyphosate, dicamba, and 2,4-D applied singularly and in combination with each other. Each herbicide combination was applied with three application methods: tank mixture, sequential applications where the synthetic auxin was applied first (auxin applied first), and sequential applications where glyphosate or clethodim was applied first (auxin applied second). The auxin applied second method had higher visual estimations of control ratings and lower biomass weights compared to the other two methods. The auxin applied second method had more glyphosate and clethodim detected with the use of liquid chromatography tandem mass spectrometry.