Poa annua CONTROL AT GREEN BAY CC

Poa annua Control Trials at Green Bay C.C.

Marc Davison, CGCS

Green Bay Wisconsin

Green Bay Country Club is 16 years old. I have been working hard trying to keep the Poa annua out, or at least under control, since the course was built. I have used Prograss, Velocity, TGR, Cutless, and pre-emergence herbicides, etc. over the years. Nothing has ever convinced me to keep going on a program because of the poor results I always get. Half our fairways were originally seeded to Pennway creeping bentgrass and the second half to Providence creeping bentgrass. In 2009 we had approximately 5% Poa annua.

During the summer of 2009, I decided to get as aggressive as I have ever been. On May 22, 2009, I treated all of our fairways with a full rate of TGR 31-3-6. That is 32 oz/ac of Paclobutrazol and 0.85 lb. N/1000 ft². That was the first time I ever applied that much TGR over all of our fairways.

In July, I started applying Velocity at various rates and at various frequencies. I wanted to incorporate all the different approaches I have read about, including the “quick reduction” and the “slow reduction” programs. I applied Velocity twice at a 6 oz/acre rate and 14 days apart on six fairways. I followed these applications with 2oz/acre Velocity, also on two week intervals. In total, I ended up with a few fairways. receiving 14oz/acre (6+6+2 oz), a few fairways getting 18oz/acre (6+6+2+2+2 oz), one fairway just got the two 6 oz. applications. Thirteen fairways received no Velocity.

One of my 18 oz/acre fairways also got a second application of TGR on Aug. 18^th at full rate. This fairway received a total of 64oz/acre paclobutrazol and 18oz/acre Velocity. This fairway was treated with the highest rate of chemical of any fairway in the trial.

My observations in 2009:

1. There were several interesting color changes in the fairways. The Velocity turned the bentgrass a very lime green color, which is not a problem unless you skip an area. Then the color difference is obvious.

2. The Velocity treated fairways looked very droughty towards the end of summer. Kind of sick and worn out looking.

3. I did not observe any noticeable differences in Poa annua populations between any of the treatments in the fall of 2009.

In the spring of 2010, I was hoping to see some real differences in Poa annua infestation among the fairways. I waited until seed head formation before drawing any conclusions. The spring of 2010 has been a banner year for seedhead formation on the Poa annua. Unfortunately, I could see no difference in Poa annua infestation between the untreated fairways and any of the treated fairways.

The only place that I noticed any damage to Poa annua was on small areas of three of the greens. It took a month before I figured out what had caused this. While spreading TGR on our green collars last summer, I grabbed handfuls of the material from the spreader and hand sprinkled it directly on the small Poa patches in these three greens. I saw no ill effects last summer or fall, but this spring it was obvious something had been applied in these specific areas.

What are my plans during the 2010 season? I am going to spray 8 oz. paclobutrazol and 4 oz Primo on all our greens and fairways at three week intervals beginning the week of June 7^th. I have already applied TGR 31-3-6 at half rate on all fairways.

I still am not convinced that any of this is worth the cost in labor and material. The Poa annua population keeps growing. I am willing try just almost anything, but I am unwilling to waste money if it’s not working.

I would like to hear from other superintendents concerning their experience in controlling Poa annua.

I can be reached at:

mdavison@greenbaycc.org

or

920-339-4640

Or you can post your results on the blog by sending an e-mail to Nick Christians at

nchris@iastate.edu.

Thanks for your time.