Annual bluegrass (Poa annua) has been a common topic of conversation this spring on golf courses across the Southeast. A warm fall followed by a prolonged, mild spring produced ideal conditions for Poa annua growth and very few courses have been spared. These weather conditions favored Poa annua over desirable warm-season turfgrasses, especially where the most effective preemergence herbicides cannot be used – like on and around putting greens or in overseeded turf. While the weather this year has been an obvious issue, many factors can contribute to poor Poa annua control. As we learn more about this problematic weed, we are learning that a comprehensive, year-round program is necessary for any hope of controlling this not-so-annual weed.
One factor that doesn’t get enough attention is the role of growing environments and turfgrass health in weed control. This was very evident at the Clemson Turfgrass Research Field Day in Florence, South Carolina. The event was hosted by Dr. Joe Roberts and Dr. J.C. Chong, while Tim Stoudemayer presented “Winter Management of Bermudagrass for Enhancing Annual Bluegrass Control.”
I always learn a lot from turfgrass field days, but the finding that really stood out to me was the impact of shade on turfgrass health, disease control, weed control and soil moisture. Dr. Roberts’ team ran a series of shade studies on ‘TifEagle’ ultradwarf bermudagrass where shade was applied only in July and August of 2020 and 2021. The plots were in full sun for the rest of the year. The impact of the shade treatments was still very evident in April of 2022. Shade decreased overall turfgrass quality and Dr. Roberts’ team also saw an increase in pythium blight, dollar spot, soil moisture and Poa annua in these plots. We are constantly reminded that while trees are important aspects of the golf experience at many courses, shade can lead to poor turfgrass quality and playability with increased disease and weed occurrence over a long time horizon.
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, Ph.D., agronomist – jbooth@usga.org