Multi-Year Fall Applied Methiozolin (‘PoaCure’) For Poa Annua Control On Golf Greens

William J. Johnston and Charles T. Golob
Dept. of Crop and Soil Sciences
Washington State University

Creeping bentgrass (Agrostis stolonifera L.) golf greens infested with annual bluegrass (Poa annua L.) can be hard to manage, unattractive, and have reduced playability.  Methiozolin (‘PoaCure’) is a relatively new isoxazoline herbicide that has shown selective P. annua control in golf greens. 

Our objective was to evaluate multi-year, single fall applications of PoaCure to control low populations of P. annua in bentgrass greens.  Research was conducted on ‘T-1’ creeping bentgrass, sand-based greens (< 5% P. annua) at the Palouse Ridge Golf Club in Pullman, WA. 

A group of superintendents learn about methiozolin field trial results at the 18th green of the Palouse Ridge Golf Course during the 2012 WSU Turf Research Field Day in Pullman, WA

A single application of PoaCure was applied at 1 or 2 fl oz/M (M = 1000 ft2) in late September, mid October, or early November 2010 (3 week intervals following initial application) and reapplied to the same plots in 2011.  The study was repeated on a separate green during 2011-2013.  The experimental design was a randomized complete block with three replications.  Initial plant counts/ft2 (two random counts per plot) were made in September at the time of the initial application and subsequently monthly during Spring and Summer of the following two growing seasons. 

In the non-treated control, P. annua increased by 61% in the 2010-2012 study (Fig. 1) and by 113% in the 2011-2013 study.  P. annua was completely controlled in the 2010-2012 study by 2 fl oz/M application made 28 Oct. 2010 and reapplied 2 Nov. 2011 (Fig. 1).  All treatments (except for the late September PoaCure application at 1 fl oz/M during 2010-2012 reduced P. annua compared to the non-treated control.  In the repeat study, a single application of 2 fl oz/M on 2 Nov. 2011 reduced the P. annua population by 73% the first year (2012) and by 80% after two years (Fig. 2). 

There was no creeping bentgrass phytotoxicity observed at any time during either study.  Multi-year (2 year), single Fall applications of PoaCure provided excellent control of P. annua; in general, P. annua control increased with PoaCure rate and late applications in the Fall.  PoaCure has the potential to become a management tool to mitigate the invasion of P. annua into newly established bentgrass golf greens or to control P. annua where a low population currently exists.  Additional research is currently underway at Washington State University to determine effectiveness of PoaCure to control higher P. annua populations in golf greens and also its effect on turfgrass quality.

Fig. 1.  Poa annua control with multi-year (2010 and 2011), single fall applications of PoaCure at Pullman, WA.
Fig. 2.  Poa annua control with multi-year (2011 and 2012), single fall applications of PoaCure at Pullman, WA.

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