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ARS Home » Pacific West Area » Corvallis, Oregon » Forage Seed and Cereal Research Unit » Research » Publications at this Location » Publication #412463
Research Project: Optimizing and Stabilizing Economic and Ecological Sustainability of Pacific Northwest Seed Cropping Systems Under Current and Future Climate Conditions

Location: Forage Seed and Cereal Research Unit

Title: A survey of ethofumesate resistant annual bluegrass (Poa annua) on US golf courses

Author
item VUKOVIC, VERA - Purdue University
item Mattox, Clint
item KOWALEWSKI, ALEC - Oregon State University
item MCNALLY, BRANDON - Purdue University
item MCELROY, SCOTT - Auburn University
item PATTON, AARON - Purdue University

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2024
Publication Date: 5/15/2024
Citation: Vukovic, V., Mattox, C.M., Kowalewski, A.R., McNally, B.C., McElroy, S.J., Patton, A.J. 2024. A survey of ethofumesate resistant annual bluegrass (Poa annua) on US golf courses. Crop, Forage & Turfgrass Management. 10(1). Article e20282. https://doi.org/10.1002/cft2.20282.
DOI: https://doi.org/10.1002/cft2.20282

Interpretive Summary: Annual bluegrass (Poa annua L.) is the most troublesome weed on US golf courses. Despite using non-chemical control measures, this weed persists requiring the application of herbicides for its control. Ethofumesate is a commonly used herbicide where cool-season grasses are grown, although there is a concern that recurring use of herbicides will lead to the development of resistant weeds. We set out to determine if annual bluegrass on US golf courses was developing resistance to ethofumesate. We tested 30 annual bluegrass populations collected from golf courses in AL, CA, IN, and OR golf courses. We found annual bluegrass populations from each state that were resistant to ethofumesate. Some had a low level of resistance while others were five times more resistant than our susceptible reference population. These results point to the need to promote diverse control strategies and a rotation of herbicides to reduce the risk of herbicide resistance development.

Technical Abstract: Annual bluegrass (Poa annua L.) is the most troublesome weed on golf courses in the US. Many agronomic practices intended to promote high-quality playing surfaces favor the growth and development of annual bluegrass, resulting in high weed pressure. One commonly used herbicide for annual bluegrass control on golf courses is ethofumesate, which is a very long chain fatty acid inhibitor. Annual bluegrass resistance to this herbicide is documented and confirmed in grass seed production systems, but potential resistance on golf courses was previously unknown. The objective of this study was to determine the frequency and magnitude of potential ethofumesate resistance from a sample of US golf courses. A dose-response experiment was initiated at Purdue University using 30 annual bluegrass populations collected from AL, CA, IN, and OR golf courses. Ten ethofumesate doses included 0, 0.56, 1.1, 2.8, 5.6, 8.4, 11.2, 16.8, 22.4, and 44.8 kg ai ha-1, with 1.1 to 2.2 as the standard label application rate for perennial ryegrass turf. A low level of resistance was found in several populations collected in each state. The mean effective dose necessary to kill 50% of the populations (ED50) was 5.7, 10.3, 3.9, and 3.8 kg ai ha-1 for populations from AL, CA, IN, and OR, respectively. The most resistant population originated from CA, with an ED50 of 14.8 kg ai ha-1. To reduce selection pressure from ethofumesate populations, golf course superintendents are encouraged to develop site-specific weed control programs that rotate herbicide sites of action, as well as utilize diverse control tactics.