Here’s a look at some of the newest weapons for the war on weeds

In recent years, several products were introduced for the control of broadleaf weeds in turfgrass. Perhaps most notable was Imprelis, sales of which were suspended in August 2011 due to concerns about possible nontarget injury on pines, spruces and other ornamental species. However, several other products successfully launched during this period, and the number of active ingredients registered for broadleaf weed control in turfgrass has doubled since the year 2000. More recently there has been a similar increase in herbicide introductions for control of key grassy weeds in turfgrass (Figure 1). This article will review some of the newer herbicides that can be used on both cool and warm-season turfgrasses. Some of these products have been available for use in turfgrass, but were only recently labeled for use on sports fields. You should always consult the label prior to use to verify that the product is safe for your type of turf.

Preemergence options

Dimethenamid-P – Marketed by BASF as Tower herbicide, this product has a supplemental label that allows its use only on athletic surfaces with warm-season turfgrass species. It is labeled for use on cool-season turfgrass used on golf courses, but not on athletic fields. One reason for this labeling decision is that dimethenamid-P will discolor but not control annual and rough bluegrass on cool-season athletic fields. On warm-season turfgrass the label also cautions not to use Tower because it will injure and thin (but not control) annual bluegrass.

Dimethenamid-P has good activity on annual weeds and is particularly effective at controlling goosegrass. It also provides a relatively quick reseeding interval of six weeks.

Prodiamine + Quinclorac – While control duration varies among products, one disadvantage of using a preemergence herbicide to control crabgrass is that the residual activity is not adequate to last the entire season. On the other hand, a postemergence herbicide application for crabgrass control is often less effective than desired if the crabgrass is actively flowering or tillering. This can be partially offset by applying the postemergence herbicide earlier, while the crabgrass is still in leaf stage. However, this is a temporary solution, since crabgrass is usually still germinating and the controlled leaf stage crabgrass will be replaced by seedlings that germinate following application.

Figure 1. Several herbicides for control of grassy weeds and sedges have been introduced recently for use on sports turf, including perennial grasses such as nimblewill and annual grasses such as goosegrass and annual bluegrass.

Cavalcade PQ was introduced a couple years ago by SipcamAdvan. It combines the preemergence herbicide prodiamine with the postemergence herbicide quinclorac. If this product is used when emerged crabgrass is in leaf stage, then the emerged crabgrass is controlled by the quinclorac. In addition, the prodiamine is applied late enough that you are more likely to see residual activity that lasts for the remainder of the season.

Ideally, Cavalcade PQ should be applied when there is leaf stage crabgrass about one month after germination has started. The product can be used earlier, but that increases the risk of not having adequate residual control. Using the product later increases the odds of getting incomplete control of the tillered crabgrass. Research at Ohio State University (OSU) has shown that when applied to leaf stage crabgrass during the month of May that 85 to 95 percent control can be achieved for the duration of the season.

A note about the use of preemergence herbicides in areas to be overseeded or reseeded: If you’re thinking of applying a product that contains a preemergence herbicide to control crabgrass and other annual weeds on thin spots that you plan to overseed or reseed, think again. Along with effectively controlling weed seedlings, most of the preemergence herbicides on the market also control the seedlings of desired turfgrasses.

Table 1. Do not apply a preemergence herbecide to areas that you also plan on overseeding or reseeding unless stated in the table. Otherwise, it will be necessary to wait per the lable before seeding.

Table 1 shows the recommended reseeding interval for the active ingredients used as preemergence herbicides where cool-season turfgrasses are grown. These were taken straight from the label of a product that contains the herbicide. Note that most of the intervals are long enough that, were they to be applied in March or April, you would not be able to safely overseed until summer. We all know that summer is not a good time to overseed.

While the table emphasizes only preemergence herbicides, note that almost all herbicides have some activity on seedling turf, so consult the product label in order to avoid injuring seedling turfgrass. If you have small areas that are thin or bare, you may wish to apply the preemergence herbicide and attempt to manage the existing grass to fill in the bare spot. If it’s a large area, then you’re probably better off overseeding and avoiding herbicide use.


Photo courtesy of PBI Gordon.

An App for Weed Control

PBI-Gordon Corporation (http://www.pbigordon.com) has announced availability of its new WeedAlert mobile app. The app provides enhanced mobile functionality and access to information from the http://WeedAlert.com online weed identification and control resource.

The app features detailed color photos of more than 100 weeds, allowing turf professionals to search and identify weeds by name, appearance or region. Detailed information about each weed includes description, control options, geographic coverage maps of where the weeds grow and when they are prevalent in the various growing zones, as well as herbicide use and recommended control products.

Turf professionals may visit Visit http://www.weedalert.com using a mobile device to download the app.

Alternatively, note that the herbicides siduron and mesotrione are safe for use on seedling turf. Follow label directions carefully. When used properly, siduron will reduce crabgrass, goosegrass, foxtail and many summer annual broadleaf weeds by about 80 percent. Mesotrione will reduce crabgrass, goosegrass, sedges and summer annual broadleaf weeds by 90 percent or better. In addition, topramezone (Pylex) was recently approved for use on sports fields.

Products with pre and postemergence activity

Topramezone – A recent introduction from BASF marketed as Pylex, topramezone has a similar mode of action to that of mesotrione, the active ingredient in Tenacity. Topramezone inhibits carotenoid biosynthesis, which results in bleaching of affected leaf tissues. Pylex is only for use on centipedegrass, Kentucky bluegrass, perennial ryegrass, and tall or fine fescue. It’s also important to note that as of this writing Pylex is labeled only for spot treatment applications on sports turf and residential surfaces; this is articulated in a special section on the label. It’s possible that the spot application restriction will be lifted in the future and broadcast applications will be permitted.

Pylex is excellent for the control of goosegrass and sedges. In addition, research has found that it can be very effective for the postemergence control or tillering crabgrass. In trials at OSU, we found that control was similar of, in some cases, better than control of crabgrass with mesotrione or quinclorac. Pylex also has activity on perennial grassy weeds and is labeled for suppression or control of creeping bentgrass, bermudagrass, Dallis grass and nimblewill. Control of these weeds is achieved with a three-application schedule similar to that of mesotrione. Consult the label for specifics. In addition, Pylex is labeled for the control of 15 grassy and 39 broadleaf weeds.

Research to date has found mixed results with the use of topramezone for annual bluegrass control. Further work is underway to investigate different application timings and rates. For broadleaf weed control, research at OSU has found that topramezone has good activity against white clover, but is not as active against broadleaf weeds such as dandelion or ground ivy. Pylex can be applied on the day of seeding for suppression or control of germinating grassy and broadleaf weeds, but is safe to seedlings of tolerant turfgrass species.

Postemergence choices

Amicarbazone – Xonerate, from Arysta LifeScience, is labeled to control annual bluegrass and 22 other annual weeds, including on athletic turf. Research has shown some favorable results with this product. Control of annual bluegrass with any herbicide can be variable, but research has shown up to 90 percent control is possible with Xonerate. For cool-season turfgrasses, such as Kentucky bluegrass and perennial ryegrass, the label includes two application schedules, but most university research is recommending the lighter and more frequent 1-ounce application schedule and at temperatures below 85 degrees Fahrenheit. Xonerate can be used on dormant and actively growing warm-season turfgrasses; refer to the label for specific application instructions.

Flazasulfuron – This active ingredient is marketed as Katana Turf Herbicide from PBI Gordon. It received expanded EPA registration in 2013 and can be used on all professionally managed sports turf. Previously it was approved for use only on college and professional sports fields.

Toro Celebrates 100 Years

On July 10, Toro (http://www.toro.com) will celebrate a huge milestone: 100 years in business. From the start, Toro built its legacy by understanding the needs of its customers and developing products and services to help them succeed. This commitment to innovation is reflected in the more than 1,500 patents its employees around the world have earned over the years. Here’s a look at Toro’s history of innovation in the sports field management industry.

1928 -Toro introduced the Silver Flash push reel mower, billed as “America’s finest hand lawn mower.”

1930 -At the request of The University of Minnesota, Toro built a power roller for their tennis courts. The Toro Power Roller proved to be a successful product for over three decades.

1934 -Toro’s Jupiter Large Capacity Sprinkler is introduced for golf courses, polo fields and other large turf area applications.

1973 -Toro introduced a new concept in commercial rotary mowing equipment: the all-hydraulic Groundsmaster 72.

2008 -Toro introduced the all-new Toro Groundsmaster 5900 Series rotary mower, which mows an acre in less than five minutes.

2010 -Pioneering an all-new mower category, Toro introduced the Groundsmaster 360 rotary mower with Quad-Steer all-wheel steering.

It’s labeled for southern turfgrass species including bermudagrass, zoysiagrass, centipedegrass and seashore paspalum. It is not labeled for use on carpetgrass, St. Augustine grass or any cool-season turfgrass species. In fact, one of the main uses of Katana is for the selective removal of overseeded or volunteer cool-season turfgrass species, such as annual ryegrass, Poa trivialis or tall fescue, from warm-season grasses. Beyond this, Katana is registered for the control of 58 grassy and broadleaf weeds, including kyllingas, sedges and annual bluegrass. It’s primarily a postemergence herbicide, but has some preemergence activity. Be sure to consult the label prior to application, as it provides information as to the potential tolerance of your cultivar or turfgrass.

Dr. David S. Gardner is an associate professor in the Department of Horticulture and Crop Science at the Ohio State University. He teaches courses in turfgrass management, ornamental plant identification and statistics. His research focuses on turfgrass physiology and weed management.