Effect of Indaziflam Applications on Hybrid Bermudagrass Growth.

Since indaziflam’s US registration in 2010 and commercial utilization, reports of hybrid bermudagrass injury (HB) have surfaced; however, causes of HB injury are not well understood. Research to date investigating indaziflam-HB injury is limited. The objectives of this research were to determine the effects of indaziflam application timings and rates on HB growth in previously injured (PI) and previously noninjured (PN) areas. Field research was conducted from 2012 to 2014 evaluating indaziflam application rates [16 fb 16 (28 d), 33, 49 or 65 g ai ha^-1] and application timings (fall-only, fall-plus-spring or spring-only) in two systems [previously injured (PI) and previously noninjured (PN) areas following indaziflam application] to elucidate factors that adversely affected HB growth.  According to our research, indaziflam’s effect on HB growth varied based on the scenario it was applied in.  Based on the results, indaziflam applied in the fall or spring affected HB growth similarly; while yr, system and to a lesser extent application rate effected HB growth.  Overall, the PN system with suitable HB growth conditions was not adversely affected across yr or application rate; however, reduced HB cover, NDVI, root length and root mass were observed in the PI system during yr two.  This was attributed to comparatively poorer growth conditions in the PI system coupled with more severe winter weather in yr two.   Further, bioassay data suggest the HB growth reduction observed in PI system, yr two, was not primarily due to indaziflam-soil bioavailability.  Based on visual HB cover data, split applications reduced adverse effects.  Data from this research suggest indaziflam applications to established HB in areas with suitable growth conditions are safe for practitioners; however, applications in areas with poor growth conditions may provide unacceptable reductions in HB cover and should be made with caution.