Formulation and adjuvant effects on uptake and translocation of clethodim in bermudagrass (Cynodon dactylon)

The effect of formulation and adjuvants on absorption and translocation of 14 C-clethodim was determined at 1, 4, 12, 24, 48, and 72 h after treatment (HAT) in bermudagrass under greenhouse conditions. Absorption of C-14-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 C-14-clethodim absorption. When either ammonium sulfate (AMS) or AMS plus crop oil concentrate (COC) was added to the 0.12 kg L-1 formulation, C-14-clethodim absorption increased significantly at all harvest times except at 12 HAT compared with 0.12 kg L-1 formulation alone, whereas, C-14-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 C-14-absorption at all harvest times when added to 0.24 kg L-1 formulation. Most of C-14-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 C-14-clethodim; however, presence of an adjuvant increased movement of C-14-clethodim out of treated leaf. Of the absorbed C-14-label, most remained in the treated leaf C-14-clethodim that translocated out of the treated leaf remained in the shoot, and negligible amount of C-14-clethodim translocated to roots. These results demonstrated improved absorption of clethodim with formulations containing half the active ingredient (0.12 kg L-1) and inclusion of both AMS and COC.