Warm-Season Turfgrass Response to Aminocyclopyrachlor

Abstract

Synthetic auxin herbicides are widely used in the turfgrass industry due to their selective control of broadleaf weeds and safety to turfgrass species. Aminocyclopyrachlor (AMCP) is a new synthetic auxin herbicide currently pursuing registration that effectively controls broadleaf weeds. However, injury to warm-season turfgrasses has been reported. Research was conducted to investigate this phenomenon in three areas: 1) quantification of AMCP rates that lead to unacceptable turfgrass injury, 2) safening of turfgrass injury, and 3) the anatomical and morphological response of St. Augustinegrass to AMCP. Results indicate that zoysiagrass is the most tolerant of AMCP. Bermudagrass and centipedegrass have marginal tolerance relative to AMCP rates that effectively control weeds. St. Augustinegrass is the most sensitive of AMCP. Attempts to safen or reduce turfgrass injury through tank-mixing AMCP with various agrochemicals were unsuccessful. The anatomical response of St. Augustinegrass to AMCP is similar to the response of eudicot weeds to other synthetic auxin herbicides and is characterized by vascular inhibition and deleterious growth stimulation.