North Carolina State University (NCSU) hosts one of the largest turfgrass field days in the country, which means it is a great opportunity to network and pick up some useful information. During the 2021 NCSU Field Day, the topic that I found most interesting is one of the largest problems facing the golf turfgrass industry in the Southeast – herbicide resistance.
Dr. Travis Gannon presented his team’s work on herbicide resistance in Poa annua. Dr. Gannon is part of the Resist Poa team of 16 scientists from across the country, working together to limit the impact of annual bluegrass as a weed in turfgrass. Dr. Gannon and his two graduate students, Tripp Rogers and Mathieu LeCompte, outlined this important research. LeCompte is a former golf course superintendent, responsible for the renovation and revitalization of Mike Strantz’s Royal New Kent Golf Club in Virginia. He knows first-hand how problematic annual bluegrass can be for golf courses. Rogers is investigating dose response of herbicides as well as nontarget site resistance of annual bluegrass while LeCompte studies the impact of subsurface lateral movement of herbicides on annual bluegrass resistance. Here are a few key takeaways:
- Herbicide resistance is the inherited ability of an individual plant to survive an herbicide application that would kill a normal population of the same species. Resistance is primarily caused by using sublethal herbicide rates and/or repeated use of one herbicide mode of action (MOA) group.
- There are 12 herbicide MOA groups that control annual bluegrass – four preemergence and eight postemergence. Annual bluegrass has confirmed resistance to eight of these herbicide MOA groups.
- Subsurface lateral movement of herbicides can injure nontarget turfgrasses and dilute the active ingredient dose, leading to loss of control and potential herbicide resistance.
- Do not apply herbicides to saturated soils or when rainfall is forecast to prevent soil mobility.
- There will be no new herbicide MOA groups in turfgrass any time soon. Rotate herbicide MOA groups and use labeled rates of both pre and postemergence herbicides to effectively control annual bluegrass and prevent resistance.
Resistance came up multiple times at the NCSU Field Day – including Dr. Jim Kerns’ and Lee Butler’s disease management work and Dr. Fred Yelverton’s work with goosegrass control. Please do your part to prevent herbicide resistant annual bluegrass by rotating chemistries and using sound application methods to apply lethal rates of herbicides when necessary.
Southeast Region Agronomists:
Chris Hartwiger, director, USGA Course Consulting Service – chartwiger@usga.org
Steve Kammerer, Ph.D., senior consulting agronomist – skammerer@usga.org
Jordan Booth, agronomist – jbooth@usga.org