Absorption and Fate of Aminocyclopyrachlor in Bermudagrass, Bahiagrass, Cogongrass, and Tall Fescue.

ABSTRACT

Aminocyclopyrachlor (ACPC) is a hormone disrupting herbicide that controls broadleaf weeds in tolerant graminaceous species. Some questions have risen over the fate of ACPC applied at labeled rates in treated plants and the environment. Studies were performed to evaluate ACPC foliar absorption, translocation, and metabolism using radiolabeled ACPC in the following species listed from most to least tolerant: tall fescue (Schedonorous arundinaceus), bermudagrass (Cynodon dactylon), bahiagrass (Paspalum notatum), and cogongrass (Imperata cylindrica). Studies indicate that absorption varied from 24 to 192 hours after treatment (HAT) and across all species. ACPC absorption was greatest at 192 HAT and did not exceed 68% in cogongrass, the most sensitive species. Translocation did not vary significantly from 24 to 192 HAT indicating that translocation was complete 24 HAT. However, translocation did vary by species. Translocation moving out of the treated area ranged from 44% of applied ACPC in bermudagrass to 64% in cogongrass at 192 HAT. Translocation data indicate that ACPC moves within treated plants when applied to the foliage in a manner consistent with other synthetic auxin herbicides in graminaceous species. Metabolism studies indicate that no metabolites exist at 7 days after treatment (DAT), which is consistent with previous research. Metabolism studies were also carried out to 14 DAT. These studies indicate three possible metabolites of ACPC with RF values less than those of the parent compound.