Annual bluegrass (Poa annua) is especially prolific in warm-season turf across the mid-Atlantic region right now. The winter was long, cold and snowy – and as golf rounds now increase, temperatures have not been consistent enough to get warm-season turf growing in earnest. As a cool-season species, Poa annua germination begins in late summer and continues through the fall. Its growth can explode once spring temperatures rise, and by early spring many plants are producing abundant seedheads and continue to produce them well into the summer. This is why Poa annua can appear to “suddenly” dominate warm-season fairways and practice tees.
Warm-season turf like bermudagrass and zoysiagrass may be greening-up, but these grasses still haven’t fully emerged from dormancy in the mid-Atlantic. This allows Poa annua to outcompete the inconsistently growing warm-season turf, particularly in high-traffic areas within fairways, collars and practice tees where turf is thin. Shade, compaction and wear further weaken desirable turf, giving Poa annua an additional edge.
Even though parts of the region are experiencing sporadic drought, in my travels, Poa annua is still thriving and producing seed at all mowing heights. Its genetic adaptability enables it to persist and adapt to varying management regimes, making eradication difficult. Resistance is another major concern. As we learned in the Southeast, where warm-season turf is heavily relied upon, using the same herbicide chemistries over and over will result in poor efficacy. Rotating herbicide groups is important – whether you are treating many acres of fairway or just a practice tee.
On bermudagrass putting greens, Poa annua has been observed in microenvironments where shade or traffic creates openings in the canopy. Its tolerance of extremely low mowing heights allows it to remain competitive in this context. Overall, the convergence of weather, dormancy transitions, potential herbicide resistance and any disturbances from traffic or management practices explain its current prominence. Reach out to your regional USGA agronomist if you’re having Poa annua issues this spring and remember that there is not a one-size-fits-all program when it comes to control.
Northeast Region Agronomists:
Darin Bevard, senior director, Championship Agronomy – dbevard@usga.org
Elliott L. Dowling, regional director, East Region – edowling@usga.org
Brian Gietka, agronomist – bgietka@usga.org