12/31/2009 - By Harrell's

Poa Control Strategies in Fairways and Roughs

Annual bluegrass (Poa annua L.) can be difficult to control on a golf course.  In this article Bert McCarty (Professor of Turfgrass Science, Clemson University) discusses techniques for keeping it under control.

Annual bluegrass (Poa annua L.) is the most troublesome winter annual grass weed on golf courses. Its low growth habit and unique ability to thrive in moist conditions and compacted areas make golf courses ideal candidates for invasion. This article focuses on Poa control in established turfgrasses.

Non-overseeded Dormant Bermudagrass Fairways and Roughs

Herbicides and timings for postemergence Poa control in dormant bermudagrass fairways include: TranXit, Monument, Katana, Finale + Envoy, Finale alone, Kerb, Revolver, Finale + Roundup Pro, Roundup Pro + Reward, and Roundup Pro + Envoy treatments which all provide similar very good control in April whether they are applied in late December or early February. Roundup Pro alone provided better control when applied in February compared to December while Princep is better when applied in December compared to February. This might explain why some “failures” have occurred with certain products as timing may make a difference. For example, since Roundup has very short residual activity, applying it as late in the season as feasible (bermudagrass is still dormant) normally works better than applying it earlier. The opposite would be true for Princep since it works best on smaller Poa plants plus has some soil residual activity. If using simazine (Princep), two applications should be used, the first in late November followed up with an additional one about 5 weeks later. Use 1 pt/acre of a 4L simazine formulation.

Overseeded Dormant Bermudagrass Fairways

Since no single product will provide 100% control in overseeded fairways containing moderate to heavy Poa populations, courses should consider a program approach. The following components of a program approach have provided most consistent Poa control in my research. Of course, each step in the program approach adds expense.

1. Apply 0.75 lbs ai/a Barricade 60 days prior to overseeding. By itself, this treatment provides ~75% control, unless it has been used for 10+ consecutive years. To boost this percentage, read on.
2. Apply either 0.5 oz/a Tranxit 25DG, 0.3 oz/a Monument 75DF, or 9 oz/a Revolver 0.19L prior to overseeding as per their labels. This assumes you are overseeding after October 1 (preferably after October 15th), therefore, allowing as much Poa as possible to germinate prior to overseeding. Since these are postemergence herbicides, any Poa which germinates after application will not be controlled. If overseeding earlier than October 1, step 2 will have diminishing effects.
3. Apply 1 gal/acre Prograss 1.5L in early- to mid-December for early postemergence control in areas where bermudagrass always goes completely dormant. Additionally, superintendents could forgo steps 1 and 2, and make two applications of Prograss at 1 gal/acre each in late November followed by another in late December. Note the exact timing restrictions. Prograss applied earlier will cause green bermudagrass to turn dormant (no long-term problems, though). However, do not apply Prograss after mid-January.
4. In mid- to late-February, apply Velocity 17.6 WDG at 6 oz/acre when day/night air temperatures are at least 70/50 F, respectively. Note that some yellowing to the ryegrass may occur for ~5 days after application. The appropriate temperatures at the time of application are critical to ensure maximum control.

Courses which haven’t overseeded in several years may just need step 1, step 3, or step 4. If step 3 is used alone, I would recommend two applications, one in late November followed by another in late December as discussed earlier.

As Poa pressure increases, however, more steps are necessary. At a minimum, I would recommend steps 1 and 2 in heavier Poa populations. Superintendents should scout their fairways in November and early February to determine if steps 3 and/or 4 are necessary.