RESEARCH VIEWS
By: Travis Teuton, John Sorochan, and Chris Main
A
nnual bluegrass (Poa annua), or as we so affectionately know it as just poa, has traditionally been one of the hardest weeds to control in cool season grasses. Many superintendents have spent sleepless nights trying to figure out how to kill poa in their bentgrass putting greens. n the past preemergence herbicide applications of Bensumec or Deminsion and growth regulators such as Primo, Proxy, and Embark have been used to control emergence, growth, and seed head production, but have had only limited success. There are two main reason for the lack of control, one is there is no real way to reduce the seed bank once a population of poa is established and two the perennial types of poa survive summer heat stress. The combination of preemergence and growth regulators work well in not letting the poa population grow, but they don’t offer complete control. However, times may have changed with a new product called Velocity herbicide (bispyrobac sodium). Valent USA is currently seeking EPA registration for selective control of poa in bentgrass and ryegrass roughs, fairways, and tees. Velocity will not be labeled for bentgrass putting greens initially. Velocity is an acetyl lactase synthesis (ALS) inhibitor that stops the production branch chain amino acids. ALS herbicides are highly selective in the species of weeds that are controlled and turf species that are tolerant. The difference in control is the affinity of the herbicide for the particular ALS enzyme of each individual plant species. There are many ALS inhibiting herbicides, such as Manor (metsulfuron), Manage (halosulfuron), Revolver (foramsulfuron), Transit (rimsuluron), Corsair (chloroUntreated control (left) vs. 0.44 oz/A weekly 57 days after application (above).