Weed Busters

It’s time consuming and somewhat costly, but Brad Gray, golf course superintendent at Mission Hills Country Club in Shawnee Mission, Kan., uses broad-spectrum herbicides to first guard against various weeds and then to attack the intruders quickly if they appear. He adds it’s is all part of doing business.

Gray uses Eliminate for broadleaf weed control in the cool-season rough and zoysia during the summer months. He utilizes SpeedZone Southern for control of broadleaf weeds in zoysia during spring transition. Typically, he uses a blanket application of Eliminate in the cool-season rough during the late fall for control of winter annuals.

 The application is costly in materials and labor, but it is good insurance that the course will be predominantly weed-free, Gray says. “Preventative weed control is best during the late fall and post-emergent spot treatment is done during the spring and summer,” he says. “The timing of the post-emergent application is coordinated with the growth habit of the species of turfgrass – i.e. cool-season turf in spring and warm-season in summer.”

Gray categorizes this season’s weed status as “about average” at his course for cool-season rough.

On the other hand, knotweed has been problematic in the zoysia fairways, he says. Late in the spring, SpeedZone Southern was applied for control. Since that application, spot treatments with Eliminate have been utilized for follow-up treatments. “The above average knotweed intrusion is due to the fact that no pre-emergent has been applied to the zoysia fairways the past three years,” he says. “The entire course was renovated in 2006 and opened July of 2007. An application of Barricade (prodiamine) was applied in 2008, but I felt the prodiamine hindered the zoysia in creating a dense stand of turf. Problematic weeds have been knotweed in the zoysia fairways. Another nuisance is white clover.”

In general, common weed problems in warm-season turf include spurge, American burnweed, doveweed, lespedeza, sedges and kyllingas, buttonweed, dallisgrass, dollarweed, bermudagrass and chamberbitter. And in cool-season turf, dandelions, crabgrass, clovers, plantains, ground ivy, nimblewill and knotweed present challenges for superintendents.

Kevin Friesen, superintendent at Turlock Golf and Country Club in Turlock, Calif., uses a variety of herbicides for preventative and curative measures. He relies on Roundup and Reward for total weed control, Trimec for (broadleaf pests) in grass, Dimension, Barricade, Surflan and Ronstar as pre-emergents, Gallery for some pre- and post-emergent treatments on broad leaves, Revolver for cool-season grasses in warm-season turf and Q4, Dismiss, Sedgehammer and Freehand for nutsedge control.

“There’s a lot of trial and error,” Friesen says. “Some will work great sometimes, but depending on weather and application the desired effects do vary,”

Sometimes it is very time-consuming, such as when Friesen and his maintenance team applies a pre-emergent and the course receives higher-than-average rainfall. In that instance, the product is leached below an effective level and more applications are needed. “Or, we have to use contact herbicides on the escapes,” he says. “Then it gets expensive in labor and more product.”

Paul Brandenburg, superintendent at the Furman University Golf Course in Greenville, S.C., reports a troubling situation in his region. 2011 seems to have been a banner year for weeds, he says, and this trend has influenced his decision on which program to pursue.

“I am not into trial and error,” Brandenburg says of his approach to weed control. “I need stuff that I know works. We don’t have time for trial and error, as I have a small crew and limited time for spraying. It can be very time-consuming and somewhat expensive.”

Brandenburg is seeing more broadleaves and crabgrass this year. Goosegrass has also been a problem, as is kyllinga.

“I’m seeing more buttonweed this year, too,” he says. “Doveweed is starting to be a problem, as well. We are a weed farm where we don’t spray Ronstar. We also use products like SpeedZone, Dismiss, Triplet (basically a three-way product), Octane and Monument. I still like old stuff like MSMA, Sencor and Simazine.”

Bill Kennedy, superintendent at Chechessee Creek Club in Bluffton, S.C., has had a difficult year controlling Poa annua outbreaks.

“There seemed to be more than normal waves of germination and because we had a cold winter it was difficult to kill. In addition to Poa annua, we are seeing doveweed, torpedograss, sedge, bahiagrass and a fairly new weed in our area, trampweed.”

Kennedy uses a variety of herbicides, including Trimec, Monument, Blade, Iloxan, MSMA, Barricade, Ronstar and Celsius.

“I have proven results with all of these products,” he says. “It is time-consuming and expensive because of the climate we live in. We have a nine-month growing season, so it is a constant battle. We have established tolerance thresholds because perfection is unattainable. We try to prevent germination with pre-emergent herbicides, but once the weeds have germinated it is easier to control them in their early leaf stages. We do have to do follow-up treatments and we typically have multiple crops of the same annual weeds. Rain will increase weed pressure, so every year is different.”

Bryan Barrington’s weed management program at The Golf Club at Oxford Greens in Oxford, Conn., starts with Barricade flowable as a pre-emergent in roughs, bunker banks, tees and green surrounds. He employs Dimension as a pre-emergent on his course’s bentgrass fairways and tees. SpeedZone and Q4 tank are mixed with Barricade for treatment in rough areas. Barricade and Dimension are used for crabgrass control, SpeedZone and Q4 for broadleaf weeds.

“I have seen an increase in Poa trivialis in my bent fairways, so I have used Velocity at low rates to slowly eradicate it,” he says. “It is effective in its control, but I learned that in extreme temperatures and or drought situations like last season, it may be wise to ease back on the suggested program.”

Barrington worked up numbers to support the costly and time-consuming supposition concerning weed management.

“It takes about 15 hours altogether to spray all rough areas, which include hand spraying bunker banks and surround areas. Barricade costs about $33 per acre and Dimension is about $90 per acre.” But, he believes both products are cost-effective.

Weather and even some of his own management practices can play a role in the outbreak of certain weeds, Friesen says.

“Because of excessive rainfall after applications of pre-emergence, we’ve had to apply more contacts,” he says. “Some of the more selective herbicides have had weather-related challenges – sometimes they work well, other times during cool downs they are slower or ineffective.

“It seems overwatering some areas brings on more weeds, as well as in flower beds that get the soil surface disturbed,” he adds. “Also, it seems the more the turf surface is disturbed with such practices as aeration, the Poa annua especially comes through.”
 

Weighing in on weeds   

Weed problems vary considerably from region to region, says Laurence Mudge, technical services coordinator for Bayer Environmental Sciences. Other aspects such as turf types and mowing heights play roles, too.

But  weeds will grow and flourish in just about any turf type, including lower mowing heights or wetter soils. In particular, goosegrass is more prevalent in compacted soils. Doveweed, Mudge says, is troublesome to manage in the Carolinas, Florida, Georgia and the Gulf Coast states because it has a long season, not appearing above the turfgrass canopy until June and becoming a mat-forming weed until frost. It is believed it can be spread by mowing during the season and can go to seed prior to frost. The severity of doveweed can go unnoticed on golf courses because it grows under the turfgrass canopy and then becomes more severe and visually prominent as heat and humidity strike. So superintendents may not realize how bad the problem is until it’s too late.

“Tropical signal grass is another grassy weed pest that is very troublesome because there is no silver bullet to control it,” he says. “Infestations can be found on golf courses in Orlando south in Florida, but thankfully it has not yet spread outside of this area.”

True to their names, warm-weather weeds like warm weather, Mudge says, and plenty of moisture. “If they aren’t in that environment, but rather in drought conditions, the weeds won’t do as well,” he adds. “When turf is healthy and rapidly growing it is harder for weeds to break through. If the turf becomes weak and thin it makes it easier for weeds to emerge and overtake the turf.”

Weed identification is vital to ensure you know what you are facing so the proper herbicide is applied. When identifying weeds it is important to consider weed size when choosing post-emergent herbicides. Remember, read and understand product labels. Some herbicides can damage desirable turf when applied to control weeds, Mudge says.

Kathie Kalmowitz, Ph.D., BASF Professional Turf and Ornamentals technical specialist for the southern U.S. and transition zones, says each region tends to have its own unique set of issues.

For example, the Carolinas through Texas have unique weed infestations and management challenges. They can even vary by state. As you move into west Texas, New Mexico and into Arizona, superintendents may experience weeds not considered problematic in other areas, such as khakiweed.

These differences create challenges for chemical manufacturers because much of the research and development is dedicated to formulating efficacious and economical herbicides for a common spectrum of broadleaf and grass species, Kalmowitz says.

“But we also understand the need for herbicide solutions that can tackle troublesome weed species and still provide a broad tolerance on as many turfgrass species as possible,” she says.

There are a few situations where certain turf types are susceptible to particular weed infestations. For example, stressed Bermuda grass, which is most common in southern to western fairways and roughs, becomes susceptible to weed invasions.

“This type of grassy infestation can be very specific to the turf type,” Kalmowitz says. “For example, northern golf courses with bentgrass often find annual bluegrass growth in their fairways. Bentgrass doesn’t compete well with annual bluegrass, so superintendents end up having a mix of both turf types.”

Superintendents, when they choose to control annual bluegrass manage around brown outs (rapid removal of the Poa annua) and loss of large patches of turfgrass, or decide to live with the weed as part of their stand, Kalmowitz says.

Warm-season grasses under optimum maintenance can most times out compete many weeds. However, when play and overall aesthetics of the course are affected, then most weed occurrences can be managed with selective herbicides. Weed control can be very different between cool- and warm-season turfgrasses.

By referencing the warning statement on herbicide labels, superintendents can better understand what weather conditions will hinder an application. For example, extremely hot temperatures – 85 to 90 degree and higher – can lower an herbicide’s efficacy and increase the risk to heat-stressed turfgrass. In contrast, drought-stricken and stressed weeds are less likely to respond to a herbicide application. This is because weeds not actively growing and taking in moisture via active transpiration cannot absorb and transport the herbicide.

“During turfgrass drought, weeds can take over turf that is weakened from hot, dry conditions,” Kalmowitz says. “This can be seen in the South this season. In the North, excessive precipitation can provide optimal growing conditions for moisture-loving weeds to take over areas of the turfgrass.”

 Air temperature and humidity, as well as wind and the potential for drift play a role in weed outbreaks. Drift is particularly dangerous when applying a post-emergent herbicides. Drought-stressed turf is less tolerant of an herbicide application when it is hot and humid, even if its species is listed as safe on the label. When combining a post-emergent herbicide with an adjuvant, be sure to read the adjuvant’s label for weather restrictions.

“Also, we continue to see superintendents experiencing greater potential for damage to their turfgrass when multiple actives or additives are in the tank mix rather than more selective solo applications,” Kalmowitz says. “Again, the turfgrass is already under environmental stress, so caution should be rule under these conditions.”

Dean Modsell, Syngenta Professional Products field technical manage, agrees weather plays a role in weed outbreaks. But maintaining healthy turf is a major weapon in the ongoing battle against unwanted invaders.

“Really, weeds are most likely to occur when conditions cause poor growth of turf, whether it is because of weather conditions, poor fertility, disease activity or loss of turf density because of traffic from golfers,” he says.             

“There’s always an opportunity for weeds to take hold,” he adds. “Making sure your course’s turf is healthy is the most important measure you can take to prevent weeds.”

The Dirty Dozen

The Six Warm-Season Turf Pests

American burnweed Erechtites hieraciifolius Photo: Forest Plants of the SE and Their Wildlife Uses by J.H. Miller and K.V. Miller by The Univ of Georgia Press in coop with the Southern Weed Science Society.	Doveweed Murdannia nudiflora Country: United States Photo: John D. Byrd, Mississippi State University	Green kyllinga Kyllinga brevifolia Country: United States Photo: Charles T. Bryson, USDA Agricultural Research Service
Dallisgrass Paspalum dilatatum Country: United States Photo: John D. Byrd, Mississippi State University	Bermuda grass Cynodon dactylon Country: United States Photo: Gerald Holmes, Valent USA Corporation	Virginia buttonweed Diodia virginiana Country: United States Photo: Richard Old, XID Services, Inc.