Mitigation Practices to Effectively Overseed into Indaziflam-Treated Turfgrass Areas

Abstract

Indaziflam is a PRE herbicide for annual broadleaf and grass control in turfgrass systems and requires a 40-wk minimum interval between application and overseeding perennial ryegrass. Currently, activated-charcoal application is recommended to reduce that interval; however, preliminary evaluations determined activated charcoal alone was not a robust mitigation practice for successful establishment during perennial ryegrass overseeding. Field research was conducted in North Carolina and Tennessee to evaluate various mitigation practices to effectively overseed perennial ryegrass into indaziflam-treated turfgrass areas. Immediately following indaziflam application (53 g ai ha−1), two scenarios were created by delivering 0 or 0.3 cm H2O before mitigation practice. Irrigated plots were air-dried before conducting mitigation practices. Evaluated mitigation practices included scalping (0.6 cm cut height; debris removed), verticutting (1.25 cm depth; debris removed), and activated-charcoal application (167 kg ha−1 applied as an aqueous slurry in 3,180 L ha−1), evaluated individually and in each two-way combination in the order scalp followed by (fb) activated charcoal, scalp fb verticut, or verticut fb activated charcoal. Twenty-four hours after mitigation practice completion, perennial ryegrass was seeded (976 kg ha−1) and maintained as a golf course fairway. Overall, perennial ryegrass cover was reduced ≥ 93% at 8 and 20 wk after treatment (WAT) when no mitigation practices were performed. Stand-alone mitigation practices variably improved perennial ryegrass establishment; however, no practice provided acceptable results for end users. Combining mitigation practices improved overseeding establishment, most notably by adding activated charcoal application or verticutting to scalping before irrigation. Across experimental runs and locations, scalp fb activated-charcoal application before irrigation reduced perennial ryegrass cover 22 to 27% at 20 WAT. Results from this research suggest mitigation practices in addition to the currently recommended activated-charcoal application should be performed by turfgrass managers to improve perennial ryegrass overseeding establishment in indaziflam-treated turfgrass areas.