Wednesday, 27 July 2011

Bentgrass Comeback

So in the past month or so I have noticed a lot more bentgrass on our putting greens.  Maybe it is because of the extended Poa annua seed head cycle this year but I'm not totally sure.
There seems to be a lot more bentgrass (top middle) on our putting greens these days

My observations so far are only speculative as I do not have an actual number related to the amount of bentgrass vs. Poa annua on the greens (and we never have), but I do think that there is more than usual.

I have a few theories why we might be seeing a reduction in the Poa annua on our putting greens.

  1. Drier Greens:  We have been able to more diligently use and apply water to our putting greens these past few years.  With the upgrades to our green's irrigation systems we are able to more accurately and uniformly apply water.  This coupled with the use of our TDR 200 soil moisture probe we can apply water only when it is absolutely necessary.  We are able to dry the greens out without the worry of having to guess how much water is in the soil.  Poa annua loves cool wet conditions and until we got the soil moisture probe that is exactly what the putting greens had.  We erred on the side of caution and usually over-watered.  With our now much drier soil on the greens I think that the bentgrass is out-competing the weakened Poa annua.  People blame our wet climate for the reason why Poa annua does so well on our putting greens but I disagree.  During our wet season we see very little growth (if any) from the Poa.  When it is actively growing we have more or less total control of the moisture that is applied to the turf.  Even during wet years like 2011 I have noticed that we have been able to keep the soil moisture more or less drier than the past.
  2. Less Pesticides:  Poa annua is a very weak grass species and loves to get all kinds of diseases. (EDIT: I now take this last statement back.  It should read poorly managed Poa annua is a very weak grass species and loves to get all kinds of diseases.) Because of the pressures to reduce our dependence on pesticide use and the outrageous cost of applying these chemicals I think that the Poa annua is having a hard time competing against the much more disease resistant bentgrass.  I have continually been putting off fungicide applications and waiting until it is almost too late to apply the chemicals in an effort to save money.  EDIT:  So if you want to encourage bentrass, manage your Poa annua poorly and reduce your dependence on pesticides.

And all of this makes perfect sense, right?  It totally does!  The continual use of fungicides doesn't give the plant's natural defence systems a chance to fight back.  So if the grass doesn't have to fight, then any less strong species can move in and do just fine.  We see this on bengrass putting greens all the time.  This is a huge issue in North America.  People spend thousands of dollars trying to fight the Poa when it could be, according to me, the over use of pesticides that is leading to the increase in the Poa populations.  Add onto this the fact that water is a very valuable commodity these days and we as Superintendents are being forced to more diligently use our water and you get a very hostile environment for the Poa annua.

You heard it hear first!

please comment and let me know what you think!

Edit:  Do a search for Poa annua reduction on putting greens and everything that comes up has to do with "apply this" or "apply that" and you will see a reduction.  Try this......"don't apply this" and "don't apply that!"