It's seedhead time...

Casey Sheehan
Assistant GC Superintendent

As we get into another golfing season, a common question that we often hear early in the season is “why are the greens so bumpy in the spring?” This bumpiness is due to the high population of poa annua or annual bluegrass in the putting greens.  Since the annual bluegrass is an annual plant it produces seeds in the spring, even at the low mowing heights of a putting green.  As a result, these seedheads produce a bumpy and untrue putting surface.



Poa annua seedheads



In an effort to minimize the number of seedheads that the poa annua population produces, two spray applications are made in early spring.  These applications are a combination of two plant growth regulators (PGR), which over the last few years have shown to be somewhat successful in controlling the emergence of seedheads.

Since every annual bluegrass plant will not produce seeds at the exact same time the goal of these applications is to try and reduce the number of seedheads that emerge.  Therefore, when to make these applications is the most important and most difficult factor to determine in achieving a sufficient amount of control in seedhead production. 

Here at Huntsville Golf Club we base the timing of these applications on two points.  One is the visual observation of annual bluegrass seedheads in fairways and rough.  Since the grasses in these areas are mowed at a higher mowing height the seedheads emerge sooner.  The second basis for the timing of these applications is on a growing degree day model.  The model uses a mathematical equation to determine the optimal application time using a day’s average temperature and dividing that by 32.  For example if a day’s high and low are 57˚F and 33˚F, the
average is 45˚F divide that by 32 and we get a growing degree day of 1.4.  There can be no negative numbers in the model so if a day is calculated to have, for example, -1.4 the day is given a 0 for a growing degree day.  We usually start counting growing degree days in early march and we will get a growing degree day every day until we start approaching 300 growing degree days.  The latest research out of universities is to have the first application on the greens as close to 300 growing degree days as possible.  We then follow up the first application with a second, two weeks later to try and control any stragglers. 

"...seedheads produce a bumpy and untrue putting surface."

Obviously both of these techniques will not guarantee 100% control, but as it was stated before, the goal of these applications is to minimize the effects of seedheads to ball roll.  The good news is that the flush of seedheads that the annual bluegrass population produces is only temporary. As we move into the summer months the seedhead production will greatly decrease and the greens should become smoother and true.

Article written by Casey Sheehan, Assistant Golf Course Superintendent

Annual Bluegrass Weevil...

Annual Bluegrass Weevil

A growing insect problem on golf courses in northeast Pennsylvania is the annual bluegrass weevil (ABW).  Long a problem on golf courses to our north in states like Connecticut and Massachusetts, this tiny insect is now making it's way south and can now be found as far south as Maryland.




Annual Bluegrass Weevil

 The annual bluegrass weevil is unique in that it feeds almost exclusively on poa annua.  When we first saw this pest on our course, our first thought was to allow this insect to feed on the poa.  After all we were trying to get rid of the poa annua why not let this insect help us out.  As we found out however although the ABW prefers poa when the poa runs out it will feed on the bentgrass.  By the time we realized this several of our collars had been completely wiped out.





ABW damage

Since that time we have learned it is wise to treat for this pest.  To control this insect it is first important to understand its life cycle.  The annual bluegrass weevil overwinters as an adult in long grass or leaf litter along the margins of the golf course.  In the spring the adults migrate from their overwintering locations to low cut grass areas such as greens, tees and fairways.  Once there the adults lay their eggs on the leaf blades.  Then the eggs hatch, the larva burrow into the grass stems and feed from the inside out.  Damage first appears as wilt stress. When you water the grass and it does not recover, you know to look for this insect.  Because it is difficult to treat for this insect while it is feeding inside the grass stems, the best control strategy is to target the adults before they lay their eggs.  The success of this strategy is to time the insecticide application during the peak migration of the adults.  One way to do this is to use a growing degree model.  Growing degree models take the average of day time high and low and then subtract it from a base temperature of 50.  You keep a running total and when the number of growing degree days reach a certain number you treat for the adults.  This method has been very successful. 


Forsythia

Another method is to watch for when certain plants flower in the spring. This is called phenological indicators.  For annual bluegrass weevils the phenological indicator is when the forsythia is half yellow from the flowers and half green from the leaves.  We have also had good results with this method.


ABW can be a very destructive insect and requires careful monitoring to avoid turf loss.