Thursday, September 10, 2026

Bentgrass Contamination in Roughs


By now you've heard me talk about or read many articles I've written about the challenge of maintaining clean Kentucky Bluegrass/Tall Fescue roughs.  See the latest edition of The Piper if you missed it.  One of the products available to Superintendents to fight the good fight is called Mesotrione.  It's sold under the trade name, Tenacity by Syngenta  It is labeled to remove Creeping Bentgrass selectively from stands of Kentucky Bluegrass and Tall Fescue.  We spray the product annually with mixed results.  In order for the product to work, three applications are required, the first application starting now.  Timing is critically important. Unfortunately the timing doesn't bode well with our Member/Guest Tournament.  This product is not effective at other times of year.  The three applications must be made two weeks apart.  Therefore, to get the applications in before winter, we must start now.       

Mesotrione turns Creeping Bentgrass stark white.  You simply can't miss it.  This week, I started treating a couple areas on the front nine holes; mostly on #1.  Depending on the results we see, we may or may not re-sod a couple areas before the Men's M/G tournament.  I will be talking more about this in the next two weeks, so please stay tuned!  If you missed the latest Piper article, I posted it below:

Each offseason, the Agronomy team spends a considerable amount of time on the golf course resodding turf in the rough.  The question is, why do we bother continuing to do this if it's a losing battle and the Creeping Bentgrass and Poa annua that comprise a lot of our rough, will only return?  It’s a valid question but one with several answers.  First, it’s important you understand these grasses and how the weather plays in this.  For the sake of this article, I am going to refer to Creeping Bentgrass as CBG and Kentucky Bluegrass as KBG.  When Bentgrass (CBG) is growing in the rough, it thrives in wet conditions compared to Kentucky Bluegrass (KBG), the desired species for our rough that does better in sunny, dry and well drained environments.  Knowing Highlands weather like you do, you can see CBG already has a competitive advantage here over Kentucky Bluegrass (KBG).  You also know that our climate is extremely mild compared to other “cool season” climates in the country.  This allows any grass that germinates in the rough to survive.  In other areas of the country, CBG cannot survive the hot and dry summers in the rough, where irrigation coverage is somewhat limited compared to fairways, for example.  Therefore, a young CBG plant never gets the chance to establish.  In our Highlands climate, it is given the opportunity to thrive simply based on mild temperatures and excessive rainfall.  All this said, the life of Kentucky Bluegrass sod at Highlands CC can last anywhere from 3 years, up to 7 years before the contamination of other turfgrasses requires it to be resodded again.

 Everyone loves the clean look of KBG rough.  It provides a beautiful contrast between a lime green CBG fairway and the dark green rough.  From a playability standpoint, a golf ball also sits up on it so nicely compared to 2-3" tall CBG, where the ball settles down into the turf.  This makes for a very difficult shot as we’ve all experienced. 

 Agronomically speaking, CBG in the rough comes with its fair share of challenges as well.  Both Bentgrass and Poa annua are far more susceptible to fungal diseases, heat stress and insect pressure.  This means that they require a lot more inputs like fungicides, to remain looking good.  Even in the photo below, this area has received four fungicide applications this year to date, and the Poa annua and CBG are still struggling.  When we have warmer and dryer summers, like 2026 has been, we are challenged with the task of keeping the CBG in the rough alive.  As hard as we try and the more resources we throw at it, it’s still nearly impossible to keep up with it.  The turf doesn't look good and still requires us to apply chemical treatments that KBG does not require.  So, another reason why re-sodding roughs is important is that KBG rough saves resources and reduces chemical inputs.

 There remains one more major reason why CBG dominates roughs, and it begins every spring when we start getting the occasional 50*F warm day and turf begins waking up from winter dormancy.  CBG and Poa annua have about a one-month or more head start on the Kentucky Bluegrass, which requires much warmer temperatures for growth.  CBG and Poa annua are the two grasses in the cool season family that wake up first following a long winter.  During this time, these unwanted grasses have a competitive advantage and use it to their benefit.  During the entire month of April, while KBG is still relatively dormant, the CBG is busy creeping overtop of the KBG.  This is the time of year when CBG gains the most traction, in my opinion.  The same phenomenon happens in late autumn, when temperatures cool enough to shut down KBG, but CBG is still in a state of active growth.  

 Hopefully by now, you can clearly see that Highlands’ climate of mild temperatures and abundant rainfall, CBG and Poa annua are always going to be a challenge in the rough. So far I have identified two reasons why a pure stand of KBG is important in the rough.  The issues we face with CBG in the rough affect both aesthetics and playability. 

Every year, we allocate about $70,000 to our operating budget to replace the rough in the worst areas on the golf course.  $70,000 is enough money to approximately re-sod the rough on one golf hole, the average length of a par 4 hole, specifically.  We prioritize the areas where playability is a major factor or areas that are visually not as attractive as they could be.  We also try to use these funds by re-sodding large areas rather than small areas here and there.  This allows us the ability to apply an herbicide, known as Tenacity, that selectively removes CBG from a stand of KBG or Tall Fescue.  The chemistry isn't perfect and only about 60% effective, but it does help prolong the life of the KBG before it needs to be resodded.  We've been using this product for many years, and you would know it because it turns the Creeping Bentgrass bright white in color, in the fall, before it dies. In fact, we’ll be starting those applications in mid to late September when soil temperatures cool into the 50’s.  This chemical requires three total applications, at two-week intervals.

Speaking of weather, 2026 has been one of the dryest on record.  At the end of August, we remain 24” below average for 2026 alone.  When you combine 2025 and 2026, we are 44” below average!  While it seems like 2026 has been rainy, the rain totals we receive are often minimal and not the typical Highlands rain events we are used to getting.  But, we all know that can change any day and we’re excited to see what Mother Nature has in store for us this fall.  In the meantime, continue to enjoy your golf course and from my entire staff, we are most appreciative of your continued support!