|Koger Iii, Clifford|
Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2006
Publication Date: 3/10/2007
Citation: Nandula, V.J., Poston, D.H., Reddy, K.N., Koger Iii, C.H. 2007. Formulation and adjuvant effects on uptake and translocation of 14**c clethodim in bermudagrass (cynodon dactylon). Weed Science 55:6-11. Interpretive Summary: Clethodim is a commercially available postemergent grass herbicide registered for use in cotton and soybean. A new formulation with half the active ingredient is under commercialization. Scientists from Delta Research and extension Center, Mississippi State University and Southern Weed Science Research Unit, Stoneville, MS have examined the efficacy of two formulations on bermudagrass and effect of adjuvants on uptake and movement in bermudagrass. Clethodim uptake with the lower concentration formulation was higher than with the higher concentration formulation. Adding either ammonium sulfate (AMS) or AMS plus crop oil concentrate (COC) increased uptake. Most of clethodim remained in the treated leaf, and formulation did not have an impact on distribution of clethodim, but adding an adjuvant increased movement of clethodim out of treated leaf. These results suggest increased herbicidal efficacy can be attained with a more dilute formulation containing a suitable adjuvant (AMS and COC).
Technical Abstract: The effect of formulation and adjuvants on absorption and translocation of 14C-clethodim was determined at 1, 4, 12, 24, 48, and 72 h after treatment (HAT) in bermudagrass under greenhouse conditions. Absorption of 14C-clethodim with the 0.12 kg L-1 (15 to 85%) formulation was higher than with the 0.24 kg L-1 (5 to 40%) formulation, regardless of presence or absence of adjuvant. There was considerable variation in the effect of adjuvant on 14C-clethodim absorption. When either ammonium sulfate (AMS) or AMS plus crop oil concentrate (COC) was added to the 0.12 kg L-1 formulation, 14C-clethodim absorption increased significantly at all harvest times except at 12 HAT compared to 0.12 kg L-1 formulation alone, whereas, 14C-clethodim absorption after addition of COC to the 0.12 kg L-1 formulation was similar to the 0.12 kg L-1 formulation alone up to 24 HAT. Conversely, COC enhanced 14C-absorption at all harvest times when added to 0.24 kg L-1 formulation (10 to 40%) compared to 0.24 kg L-1 formulation applied alone (5 to 33%). Most of 14C-clethodim (79 to 100% of absorbed) remained in the treated leaf independent of formulation or adjuvant. Formulation did not have an impact on distribution of absorbed 14C-clethodim; however presence of an adjuvant increased movement of 14C-clethodim out of treated leaf. Autoradiograms indicated that 14C-clethodim did not translocate appreciably to all parts of the plant. Of the absorbed 14C-label, most remained in the treated leaf. 14C-clethodim that translocated out of the treated leaf remained in the shoot and negligible amount of 14C-clethodim translocated to roots. These results demonstrated improved absorption of clethodim with formulation containing half the active ingredient (0.12 kg L-1) and inclusion of both AMS and COC.