One of my favorite parts of traveling early in the year consulting with golf courses is responding to the question, “What are you seeing?” This year my number one response is, “Poa annua - and I’ve seen plenty.” My comments usually are met with a nod of the head and some variation of “I thought we were on top of it until mid-March and then it was everywhere.”
As I think about why Poa annua breakthroughs happened, there are a few threads that most situations have in common:
- Some amount of herbicide resistance
- A switch to a midfall program that combines a preemergence herbicide with one or more postemergence herbicides
- No midwinter cleanup with a nonselective herbicide because the turf management team was hopeful that the midfall application would keep the course relatively free of Poa annua until spring
So, what to do if Poa annua breakthrough has occurred at your course? By April to early May, it is pretty much game over for using a herbicide to kill mature Poa annua plants. Warm weather and mowers are the best short-term control strategy but they require patience and a multiweek time horizon. Longer term, there are a couple of steps to take. First, evaluate what went well and what didn’t with your weed control program. This will lay the groundwork for next year’s plan. Second, take the time to review the resources on resistpoa.org. This site contains the work of 16 scientists who have come together under one USDA grant to study Poa annua herbicide resistance, biology, control constraints and best management practices. And who knows, maybe next year the story will be about what I’m not seeing – Poa annua breakthrough!
Southeast Region Agronomists:
Chris Hartwiger, director, USGA Course Consulting Service – chartwiger@usga.org
Steve Kammerer, Ph.D., senior consulting agronomist – skammerer@usga.org