Utilizing Flumioxazin for Annual Bluegrass (Poa annua) Control in Bermudagrass Turf

Abstract

Annual bluegrass is a problematic weed in bermudagrass and other intensively maintained turfgrasses. Flumioxazin is reported to control annual bluegrass both PRE and POST; however, as a contact herbicide, flumioxazin injures actively growing bermudagrass. Research was conducted in Alabama and California to evaluate optimal flumioxazin application timing for annual bluegrass control, bermudagrass response, and overall sward quality in the field, and to assess annual bluegrass control at various growth stages in the greenhouse. November and December application timings resulted in the best balance of the three parameters. When bermudagrass was not dormant at application, treatment resulted in necrosis of green tissues and thus induced dormancy. The herbicide-induced dormancy resulted in better sward quality due to more uniform and therefore more aesthetically pleasing dormant turfgrass relative to natural dormancy. Flumioxazin at 0.43 kg ai ha−1resulted in better annual bluegrass control and improved sward quality relative to 0.21 kg ha−1. Incomplete POST annual bluegrass control from later applications was attributed to larger weed size, limiting the effectiveness of this contact herbicide. Greenhouse data corroborated field results and indicated that flumioxazin at 0.43 kg ha−1controlled ≥ 95% of annual bluegrass up to two tillers. Flumioxazin can be utilized for PRE and POST annual bluegrass control, but utilization of this herbicide is limited to dormant bermudagrass unless induced dormancy can be tolerated, and POST control is limited to annual bluegrass plants ≤ two tillers in size.