Preventing Poa annua INVASION When to fight and when to give in By Katerina S. Jordan, PhD A lmost all Canadian golf course greens are seeded to some cultivar of creeping bentgrass (CBG)—Agrostis stolonifera. This species is the most logical choice due to its ability to tolerate very low mowing heights, as well as its tolerance to traffic, repeated mowing, drought, heat, and cold. It also makes an excellent playing surface when properly maintained. However, most golf course greens within 10 years end up with some annual bluegrass (ABG)—Poa annua—in varying proportions in the mix. Although the playability of mixed bentgrass/bluegrass greens can be very good, there are other issues that arise when Poa annua becomes a dominant part of the mix. These can include: • decreased drought tolerance and winter hardiness (Figure 1, page 12); 1 • increased disease and insect pressure (Figure 2, page 12); and 10 January 2013 CG_Jan2013.indd 10 1/17/13 1:30:44 PM