Poa annua seedhead reduction/prevention

 One of our more important programs for spring golf in our area is an application of growth regulators to reduce the effects that tiny poa annua seedheads have on ball roll and smoothness of our greens.

Poa annua with seedheads.

We utilize an internet site which helps us count  growing degree days which are used for the timing of various applications to reduce the impacts of certain weeds, diseases, and insects.  The 32 degree day model is used widely to determine when to spray our products to reduce poa annua seedheads.  From the modeling that I have been following over the last couple of weeks, I decided to make our application last Thursday morning.  The products that we utilize allow our greens to keep a decent color but do not totally eliminate seedheads.  Michigan States research determined that we can count on about 50% reduction in seedheads on average or better.  Our greens range from 10% to 60% in poa annua contamination.  50% or better is good on a less contaminated green but not as good on a higher contaminated green.  Other tools that are at our disposal during this period if the chemical treatments don't work as well include: 

• Verticutting which stand up the seedhead allowing the seedhead to be cut off completly.
• Topdressing and brushing which keep the surfaces smoother and cut off excess plant material
• Additional growth regulators which keep the poa plant weakened and shortened.

What is a growing degree day?  The high and low temperatures of the day are added together and are then divided by 2 to get the average temperature for the day.  I.E.,  our weather station reported a high of 67 and a low of 52 which is a total of 122.  Divide 122 by 2 and you get 61(Average temperature for the day).  Subtract 32 from 61 and you get 29 degree days.  The degree day count in our area usually begins between  mid-February to the 1st of March.

Over the years, scientists have looked at how temperatures trigger pests to begin their process which create havoc on turfgrass.  This can include egg laying of insects to seedheads forming on poa annua to disease models for spraying early season preventative applications of summer root diseases.

Ohio State University has an informative explanation on the growing degree day model as well.

A current picture of poa annua on our practice green without seedheads.