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Poa Annua Seed Head Control at Des Moines Golf & Country Club

March 22, 2012

This article comes to us from Rick Tegtmeier, CGCS, Des Moines Golf & Country Club.

At DMGCC, we are like many other golf courses in Iowa, we have poa annua and we try to control the ugly seed heads that emerge in the spring. Many different types of growth retardants are used and we are no different. We use a combination of Primo and Proxy to control our seed heads. When we spray it on our fairways we use the following rates of PGR: Primo at 5 oz per acre (.11 oz/1000) and Proxy at 220 oz per acre (5 oz/1000). This is commonly referred to as the 5 and 5 program.

One thing we all struggle with is to when we start spraying the turf. In the case of poa annua seed heads, control must be done well ahead of the emergence of the seed head from the sheath area of the plant. We have found that using a Growing Degree Calculator has been our best tool to get the timing correct on when we do our first spray. I use a simple Excel spreadsheet to enter my daily temperatures and it automatically figures the cumulative total of Growing Degree Days.

My good friend Steve Cook, CGCS, MG,Director of Agronomy at Oakland Hills Country Club wrote an explanation on Growing Degree Days for his membership and I have included a little bit of that here. One thing to note is to make sure you know what model (base) of GDD calculator you are using. We use the 32 degree base at DMGCC and some people use the 50 degree base. Just make sure your cumulative days match your model!

Here is Steve’s explanation of GDD and how it affects the plant:
The growth rates of many biological organisms are determined by temperature. As temperatures increase, activity increases. One of the ways we measure the biological activity of plants and insects is Growing Degree Days or GDD. Knowing the GDD allows us to monitor a specific number and apply plant protectants (like insecticides) at the appropriate time in an organism’s life cycle to maximize control. It has applications for plants like crabgrass or poa annua as well. What is GDD and how is it calculated? We assume that an organisms growth rate increases as the temperature rises above a predetermined base temperature. Each organism may be given a specific base temperature. Knowing these activity thresholds is important and we monitor them depending on our target pest and optimal treatments.

This year the timing is much earlier than we normally spray. We do 2 sprays in the spring to control those pesky seed heads. There are some studies out there that advise you when to make the second application as well. This too is based on cumulative GDD’s. Until more work is done though, we will continue our program of spraying 21 days after the 1st spray. We typically apply some ferrous sulfate with the 2nd spray to mask some of the PGR effects. If you would like a copy of our Excel Spreadsheet shoot me an email and I would be happy to share it with you.

Rick Tegtmeier, CGCS
Des Moines Golf & Country Club


Annual Bluegrass: Friend or Foe?

May 23, 2011

Frenemy – a blend of the words “friend” and “enemy” that refers to an ally who is simultaneously a rival. An example of such would be Dwight Schrute and Jim Halpert in The Office, or two teammates fiercely competing for a starting spot. In a turfgrass sense, Poa annua and I are frenemies.

Here in the Midwest, Poa is an enemy: a weed with poor roots and annoying seedheads. However, it provides an unmatched playing surface in a temperate climate. In fact, you can even be Poa annua’s friend on Facebook.

My golf and turf management background has mainly been in Iowa, so I’ve become familiar with the differences in appearance, playability, and management of an entirely bentgrass green and a heavily Poa infested green in this region. The winter annual tolerates stress just enough to be a problem, but it can't withstand the conditions bentgrass can.  Therefore, it remains a weed.

Turf managers and golfers have a much different experience in a climate that Poa is better suited in. I’ll never forget my first time playing on an entirely Poa green in Northern California. The turf was so finely textured it was difficult to see individual leaf blades. In addition, the greens rolled incredibly fast yet surprisingly true.

That experience led me back to the Pacific Coast for a summer internship where I gained a new perspective of Poa. I was amazed to see the greens mowed at less than 0.09 inches, aggressively verticut biweekly, dried out for weekend play, and yet the turf bounced back quickly. If Poa was improved to tolerate adverse conditions and could be utilized on golf courses everywhere, superintendents would no longer need to fight it as a weed. This may be possible considering the plant's great ability to adapt.

Dr. Don White at the University Minnesota has research reports on Poa annua dating back to 1985 and has a breeding program there. Dr. David Huff at Penn State University has also been breeding annual bluegrass since 1994. Even so, a uniform supply with traits that increase stress tolerance is still not available.

Breeders have a difficult task in commercially producing annual bluegrass. Seeds are difficult to harvest because Poa annua has a plastic phenotype (one that can change). The desirable grass plant at low mowing heights produces an undesirable seed when the plant grows tall enough to be harvested. Propagating the grass from seed may not be realistic for another reason: Poa established from seed often sprouts seedheads at green height, which requires growth regulator to inhibit them from forming. Vegetative propagation of the turf is also difficult.

Imagine for a minute that Poa has successfully been bred to be used commercially for golf course greens. The limited rooting depth issue could possibly be alleviated with a shallower rootzone, allowing the water table to perch with less irrigation. This and other cultural practices can only be researched and implemented if Poa can be commercially produced. Somewhere down the line, genetic resistance to Anthracnose or tolerance to cold and heat may even be developed.

Superintendents will be managing Poa this year, but they will still be treating it as a weed. There is, however, validation in breeding it. Most people consider annual bluegrass an enemy. I, on the other hand, have an optimistic view of the plant.  This leaves Poa annua and I as frenemies.