Flumioxazin provides PRE and POST, annual weed control in dormant bermudagrass, but applications during active growth may be injurious. Flumioxazin could also provide an alternative chemistry for POST annual bluegrass control in other turfgrasses, but research is limited on tolerance levels. The objective of this research was to evaluate tolerance of five warm-season turfgrasses to flumioxazin applied at various rates and timings. Late-winter applications of flumioxazin at 0.21, 0.42, or 0.84 kg ai ha−1 caused acceptable (< 20%) injury to bermudagrass, seashore paspalum, St. Augustinegrass, and zoysiagrass at 3, 6, and 9 wk after treatment (WAT) in both years. In 2012, late-winter applications to centipedegrass caused unacceptable injury at 6 WAT, but turf recovered to acceptable levels by 9 WAT at all rates. Applications made during active turfgrass growth caused unacceptable initial injury to all species. However, bermudagrass, seashore paspalum, St. Augustinegrass, and zoysiagrass recovered to < 20% injury by 9 WAT from all rates. In 2012, centipedegrass treated in midspring had 0, 24, and 74% injury from flumioxazin at 0.21, 0.42, and 0.84 kg ha−1, respectively, at 9 WAT. In 2013, midspring applications to centipedegrass caused 13, 48, and 71% injury from 0.21, 0.42, and 0.84 kg ha−1, respectively at 9 WAT. Overall, flumioxazin has the potential to control annual weeds in bermudagrass, seashore paspalum, St. Augustinegrass, and zoysiagrass with late-winter applications before greenup, but all turfgrasses may be excessively injured during active growth.

Synthetic auxin herbicides are widely used because of their effective control of broadleaf weeds and safety in many turfgrass species. However, two synthetic auxin herbicides, triclopyr and aminocyclopyrachlor (AMCP; DPX-KJM44), are known to injure warm-season turfgrasses. Our objective was to quantify this injury through evaluations of turfgrass quality and turfgrass green cover in response to herbicide treatment. The results of this study indicate that relative to the labeled use rates of triclopyr (0.56 to 1.12 kg ae ha−1) and AMCP (0.053 kg ai ha−1), zoysiagrass is the only turfgrass tested with sufficient tolerance to the respective compounds for their use as weed-control agents. Bermudagrass and centipedegrass may be injured by triclopyr and AMCP at labeled rates, characterized by a reduction in turfgrass quality and green cover. St. Augustinegrass is not tolerant of either triclopyr or AMCP at labeled rates.