Golfdom, June 2014

Super Science healthy competition Pursuing Poa annua free cool season fairways By Zac Reicher Ph D A ll golf courses regardless of budget struggle to minimize Poa annua in fairways Thinning or complete death of Poa annua in summer or winter plus additional damage to the desired species inevitably leads to reseeding the desired turf However Poa annua quickly germinates when favorable weather returns and it aggressively out competes seedlings of the desired turf Often the end result is higher populations of Poa annua than were originally present Fig 1 Tis cycle may repeat itself annually in areas of the country with consistently difficult summers and or difcult winters However new thinking with modern herbicides may help stop this cycle TiminG of overseedinG Seeding summer thinned areas usually starts near Labor Day with the return of cooler temperatures Though this is an ideal time to seed cool season grasses the majority of Poa annua seed in the soil will also start to germinate in mid September Kaminski and Dernoeden 2007 Te desired grass and Poa annua will be germinating at almost the same time and Poa annua will always outcompete desired turf Terefore seeding earlier in the summer is preferred to allow germination and maximum maturity prior to Poa annua seed germination Our work at Purdue showed that seeding creeping bentgrass in mid August resulted in 19 percent cover fiGUre 1 Poa annua filling in between lines of perennial ryegrass overseeded in early September in Nebraska The Poa annua will out compete the perennial ryegrass over the winter likely resulting in more Poa annua present than in the previous year of annual bluegrass by the following June with no control interventions whereas seeding only a month later resulted in 43 percent cover of annual bluegrass Furthermore Henry et al 2005 showed overseeding creeping bentgrass into an existing Poa annua green in July resulted in greater than 70 percent coverage of creeping bentgrass two years later whereas August seedings resulted in 17 percent or less coverage and September seedings resulted in eight percent or less coverage of creeping bentgrass Fig 2 Our current work at the University of Nebraska is also evaluating seeding in mid summer almost as a preventative seeding in areas that perennially thin during the summer stress Tis three year study will wrap up soon but early results indicate early summer seeding is more effective than late summer seeding for long term success especially when overseeding with creeping bentgrass More important our work is showing that following up seeding with herbicides for Poa annua control limits competition and further improves successful establishment of desired seedlings In other studies we are evaluating ratios of Kentucky bluegrass perennial ryegrass for short term cover golfer satisfaction as well as aiming to maximize Kentucky bluegrass in the stand Tis study also includes aggressive use of post seeding herbicides to minimize Poa annua Early results suggest that regardless of the Kentucky bluegrass perennial 34 Golfdom June 2014 Golfdom com photo by zac reicher Overseeding and post seeding herbicides