Although winter is coming, it's not too soon to think about things to improve in 2014. Annual bluegrass (Poa annua) seedhead production is one of those annoying things that many turf managers will be facing as we come out of winter and transition into spring. Proxy (ethephon) is a Bayer Solution for reducing the impact of seedhead production. Correct timing of Proxy is critical for successful seedhead control. Recent research suggests that added early Proxy applications add extra control. To get added plant health effects, combining Proxy with Chipco Signature™ can help jumpstart spring turf quality.

Getting Down to the Business of Seedheads
Although it's often managed as a perennial plant, deep down - annual bluegrass is (by nature) an annual plant that wants to seed in the spring (as the name implies... Copious seed production by annual bluegrass contributes to its success as an invasive weed, and the white seedheads are often considered 'unsightly' in managed turf. When annual bluegrass is present on putting greens, seedhead production is blamed for poor playing conditions, bumpiness and poor ball tracking during play. Another consideration for those managing annual bluegrass is that the energy that it expends in making seeds can deplete carbohydrate reserves. This weakens the plants making them more susceptible to stress diseases such as anthracnose.

Let's Geek-Out with Ethephon: How Proxy Works
Ethephon, the active ingredient in Proxy, is a growth regulator that when absorbed by the plant is converted to ethylene, a naturally occurring plant hormone. Ethylene is involved in functions such as leaf abscission, flowering initiating and fruit ripening. For plant functions, the rate and balance between the various plant hormones (ethylene, cytokinins, auxins, etc.) triggers physiological responses. In a nutshell, ethephon applications basically throw ethylene levels in annual bluegrass 'outta whack' in order to inhibit seedhead production.

Since ethephon inhibits seedhead production, Proxy must be applied prior to the completion of the process. This is why Proxy is recommended to be applied at the 'boot' stage of annual bluegrass, e.g. it must be applied before seedheads emerge from the plant and before the plant starts focusing on seedhead development and maturation. Once seedheads have emerged, Proxy cannot effectively reverse the process.

Spring Proxy applications work best when applied at 5 fl. oz. per 1,000 sq. ft. with 0.125 to 0.25 fl. oz. of Primo MAXX, Syngenta's popular plant growth regulator that inhibits gibberellic acid production. The combination provides the best overall seedhead suppression and turf quality when applied to actively growing plants.

Doing the Da' Boot: Proper Timing of Proxy Applications
As mentioned above, early applications to seedheads that are being produced by the plant are essential, e.g. during or prior to the boot stage. Physically looking for the boot stage in plants is possible but you'll need a macroscope or magnifying glass to get a good look. That's painful, and impractical in most cases.

Other ways to estimate the boot stage of annual bluegrass is to look for seedheads being expressed early in south facing slopes and higher cut turf, or to use Forsythia in full bloom as an indicator plant.

Growing degree day (GDD) models offer a weather based way to time Proxy + Primo applications. In the mid-Atlantic, fifty 50 degree growing days (GDD50 = 50) seems to be the best using March 1 as a start date. There is a bunch of ways to calculate GDDs, but the folks at The Weather Channel have a nice GDD calculator at www.weather.com/outdoors/agriculture/growing-degree-days/11968 that's easy to use.

The 1st Proxy + Primo should be applied at this time and followed by another Proxy + Primo two to four weeks later for best effect.

Proxy + Primo applications may cause some discoloration or bronzing or turf when applied in the spring to actively growing turf. In most cases the discoloration is temporary and the turf should recover quickly. Turf that is stressed or damaged due to poor growing conditions is likely to show the most negative effect.

Go Early: New Thoughts on Fall and Winter Applications of Proxy
GDD models and other predictive tools aren't perfect, and often Proxy + Primo programs give variable levels of seedhead suppression year to year. Investigations by Dr. Shawn Askew at Virginia Tech suggest that early applications of Proxy about a month ahead of the 'normal' applications have an added effect and help give more consistent annual bluegrass seedhead control. Another bonus is the reduction of any discoloration or stress from Proxy + Primo applications in the spring.

For these early applications, Proxy should be applied 5 fl. oz. without Primo. Currently, Dr. Askew is looking at changing the timings of applications to include a 'pre-snow' and a 'post-snow' application of Proxy. More concrete BMPs will come out of his research when it's complete, but an added late-winter/early-spring application of Proxy makes good sense as added protection against seedheads.

Using Chipco Signature™ with Seedhead Suppression Programs

Seedhead suppression applications with Proxy + Primo can sometimes stress turf; after all you're suppressing the seedheads by throwing the plant out of whack physiologically. One potential solution for increasing turf quality during spring seedhead suppression programs would be to incorporate Chipco Signature as a pre-treatment to boost plant health and also as a cool season Pythium root rot preventive application. Apply Chipco Signature at 4 oz. per 1,000 sq. ft. 5-7 days before the first Proxy + Primo application and again in between the next Proxy + Primo application as a way to pre-treat annual bluegrass for stress and diseases.

Spring Can't Come Soon Enough, But I'll Pass on the Seedheads
Proxy is a valuable Bayer Solution for controlling annual bluegrass seedheads, and these tips can help in maximizing its use:
- Seedhead control must be done early with a preventive program
- Go about a month early with a pre-treatment of Proxy at 5 fl. oz. per 1,000 sq. ft. about a for added control
- Make the first Proxy + Primo at GDD50 = 50 and repeat 2-4 weeks later
- Use Chipco Signature to reduce plant stress to minimize the negative impact of any seedhead control program

Have a great Holiday Season and best of luck with seedhead control programs come this spring.