COURSE CARE
Necessary Weed Control Measures This Fall September 20, 2011 By Darin S. Bevard

During the heat of the summer, bermudagrass populations will expand into areas of weak turf or bare ground.  Control of bermudagrass in cool-season fairways is extremely challenging. 

 

The first real cold front of the fall season swept through the area in the past week, bringing in much cooler temperatures.  This is welcome relief for the grass in what has been a long, and for much of the time, hot growing season.  Fall offers the opportunity for some of the best golf course conditions of the season. 

With shorter days and cooler temperatures, turf growth is slowing rapidly.  Unfortunately, rainy weather patterns have limited opportunities to consistently groom fairways and greens for optimum playability.  Temperatures are more favorable for cool-season grasses, but under wet conditions, mechanical damage can occur.  Thus, with wet weather, it may be necessary to suspend mowing until turfgrass areas dry out.  These delays in mowing can be difficult to implement, but this will prevent rutting of turfgrass areas and other damage.  Be patient, and don’t inflict damage on yourself.

One area of difficulty in 2011 has been weed control.  Oftentimes, weed control is an afterthought.  In the past, preemergence herbicides in the spring, along with one or two broadleaf applications, were made per growing season and the golf course was reasonably well weed free.  This has been changing in recent years, with increasing populations of more difficult-to-control weeds that have proven to be far more challenging to control.

Of greater concern are the increasing populations of nuisance weeds that have proven difficult to control.  Bull paspalum (not to be confused with Seashore Paspalum) and kyllinga are becoming more widespread.  Control in cool-season grasses is especially difficult, and herbicides often cause temporary thinning and/or discoloration of cool-season grasses.  Remember, these weeds are perennial in nature.  If control programs are not implemented, they will return next year and populations will increase over time.  Bermudagrass populations have also increased on many cool-season golf courses in the past two growing seasons with the extreme hot weather.  Bermudagrass populations take advantage of thinning of cool-season turf and often expand into voids that occur during the summer.

In cool-season fairways, eradicating bermudagrass is time consuming and costly.  This is especially true in creeping bentgrass fairways.  “What are we going to do about bermudagrass?” is a common question.  We see instances where bermudagrass is not killed with multiple applications of non-selective herbicides in fairways.  This has even been the case when the treated area is stripped and resodded with creeping bentgrass.  Maybe there is a message there.  However, anybody reading this update needs to realize that if controlling bermudagrass in cool-season grass was easy, the problem would not exist!

The bottom line is that weed control is becoming more difficult in many respects, especially in cool-season grasses.  Golfers should expect more discoloration from herbicides to control these emerging weed problems, or expect these problems to expand.  Often, multiple herbicide applications will be needed.  In the case of rogue bermudagrass in fairways, eradication has proven very difficult without significant disruption to the appearance and playability of the golf course.  Weed control may require increased focus going forward.  Keep in mind the fall is a good time for traditional broadleaf and clover weed control programs.

The Mid-Atlantic Region agronomists are part of your agronomic support team.  If you have a question or concern, give us a call or send an e-mail.  You can reach Stan Zontek (szontek@usga.org) and Darin Bevard (dbevard@usga.org) at 610/ 558-9066 or Keith Happ (khapp@usga.org) at 412/ 341-5922.