Regardless of your location, selection of grasses and level of expertise, at some point this season you’ll face issues with the management of weeds, insects and/or diseases on your athletic turf.

Understand that some pest problems are more common than others. In this month’s column, we’ll focus on the major — or most likely to be encountered — pests along with recommendations for how to manage them. This is not an all-inclusive list of issues that may be encountered. But the problems highlighted here occur frequently enough that you should at least be aware of them and consider if they’ve been a management issue for you in the past.

Now is the time to prepare for the season. And remember, if you’ve had issues with any of these pesky issues in the past, it’s a safe bet that you’ll want to plan to manage them again this year.

EDITOR’S NOTE: The timings listed sometimes coincide with the best time to control the specific pest, which may be different than when the pest is most likely to cause damage.

Prostrate knotweed usually precedes crabgrass germination by about three weeks. Best control is either with a preemergence herbicide or postemergence before it flowers.
PHOTO: OHIO STATE UNIVERSITY

Early spring

  • Prostrate knotweed is among the first annual broadleaf weeds to germinate in the spring, and, of course, it’s quite common on athletic fields since it’s favored by compacted soil conditions. You may also see some winter annual weeds such as henbit and chickweed.
  • Control of these broadleaf weeds can be achieved by applying a combination herbicide that contains 2,4-D, MCPP, dicamba or triclopyr, and perhaps a protox inhibitor such as carfentrazone or pyraflufen-ethyl. These weeds are best controlled early in their life cycles, before they can flower and set seed for next year’s crop.
  • When making this application in cooler temperatures, consider the use of the ester form of the herbicide, if available. Esters tend to work more effectively in cooler weather and they’re more volatile, so care must be exercised with these around sensitive ornamentals when temperatures exceed 70 degrees Fahrenheit.
  • Annual bluegrass is a winter annual that primarily germinates in autumn, but the most favorable time to attempt to control is in April. To control annual bluegrass, Xonerate herbicide, from FMC, is labelled for athletic turf. It’s used for control of annual bluegrass and 22 other annual weeds that are listed on the label. Research has shown some favorable results with the use of 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 to not apply when temperatures are too warm (above 85 degrees Fahrenheit). Xonerate may be used on dormant and actively growing warm-season turfgrasses, but refer to the label for specific application instructions.
  • Early spring may also be the time to deal with summer annual grasses, such as crabgrass and goosegrass. If your field is reasonably dense, and/or you don’t plan to do any overseeding, then the application of a preemergence herbicide, right around the time that forsythia are in bloom, is the most effective strategy to deal with these weeds. But be aware that preemergence herbicides will also prevent desirable grasses from germinating for anywhere from six to 16 weeks after application. As always, check the label for specifics.
  • All of the weeds mentioned above are favored in those areas where the turf stand is thin and not as competitive. These areas usually also have compacted soil conditions. Thus, one long-term solution is to increase the vigor of the turfgrass with proper cultural management practices, including core aeration, to alleviate compaction.

White grubs can devastate a field for two reasons. This illustrates the damage that can be caused by birds, skunks and raccoons that feed on the grubs (note that tall fescue, with a more extensive roots system, is still green in the center).
PHOTO: OHIO STATE UNIVERSITY

Late spring

  • Dandelion and white clover are examples of common perennial broadleaf weeds that will be coming out of winter dormancy and beginning to flower.
  • To control these weeds, consider the use of a postemergence herbicide containing a combination of three of these herbicides: 2,4-D, MCPP, dicamba, triclopyr or fluroxypyr. Typically, this application is made in early May. If the application is made too late, after the weeds have hardened off due to heat or drought stress, then control may not be as effective.
  • Another option for controlling dandelion and white clover is with an application of the herbicide Defendor, a newer herbicide from Dow that contains the active ingredient florasulam. This product is quite effective in cool weather and also provides good control of winter annual broadleaf weeds.
  • Yellow nutsedge is not a grass, but a sedge. Because of this, there are different herbicide recommendations for control of them. They’re easy to identify because they have three-sided stems (triangle shaped in cross section). The best control of sedges is with either sulfentrazone or halosulfuron.
  • A potential pest on athletic fields is the bluegrass billbug. The larvae are white and similar in appearance to the white grubs. But an important difference is that they lack legs.
  • As the name implies, they tend to be more of an issue on Kentucky bluegrass. The reason for this is that ryegrasses and fescues are endophytic and this symbiosis results in a certain level of protection against billbug feeding. Thus, a good way to prevent problems with bluegrass billbug is to use ryegrasses and fescues.
  • Chemical control of billbugs is best achieved with imidacloprid, thiamethoxam, clothianidin or chlorantriniliprole. These products, which are also used for grub control, should be applied in May.
  • Be aware that if using either imidacloprid or thiamethoxam, there may not be sufficient residues remaining if you also have a grub infestation in late summer. On the other hand, a May application of clothianidin or chlorantriniliprole will control both grubs and billbugs.

At right shows the turf removed and the feeding damage to the root system of the grass caused by the grubs.

Early summer

  • If you didn’t apply a preemergence herbicide and are beginning to see issues with annual grasses, June is the best time to attempt control with a postemergence herbicide.
  • A recent introduction from BASF that’s marketed as Pylex herbicide, topramazone has a similar mode of action to that of mesotrione, which is the active ingredient in Tenacity herbicide. Topramazone inhibits carotenoid biosynthesis, which results in bleaching of affected leaf tissues.
  • Pylex is only for use on centipedegrass or cool-season turfgrasses like Kentucky bluegrass, perennial ryegrass and tall or fine fescue. Also, it’s important to note that as of this writing, Pylex is labeled only for spot treatment applications on sports turf and residential surfaces. It’s possible though that, in the near future, the spot application restriction will be lifted and broadcast applications will be permitted.
  • Pylex has a broad spectrum of weeds that it’s labelled to control. It’s excellent for the control of goosegrass and sedges.
  • Research has also found that it can be very effective for the postemergence control or tillering crabgrass. In trials at Ohio State University, we found that control was similar, or in some cases better than, control of crabgrass with mesotrione or quinclorac.
  • Pylex also has activity on perennial grassy weeds and is labelled for either suppression or control of creeping bentgrass, bermudagrass, dallisgrass 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 to these, Pylex is labelled for the control of 15 grassy and 39 broadleaf weeds, both annual and perennial.
  • July is also the time to control any summer annual broadleaf weeds, such as spurge. Summer annuals can be difficult to control with herbicides, so it’s important to control them early in their life cycle.
  • Another common insect on athletic fields is white grubs, which are the larvae of different species of beetles. White grubs have a white body, tan head and three pairs of legs.
  • White grubs damage turfgrass by feeding on thatch, which results in damage to the root system. The symptoms of infestation are wilted turf that pulls up easily from severed roots. In most cases grubs aren’t present for a couple of years after a field has been established, until a thatch layer begins to develop.
  • One of the issues with grub control is that the most effective insecticides are preventative in nature. Best control is with either halofenozide or the previously mentioned products for billbug control. Clothianidin or chlorantriniliprole can be applied as early as May to also control billbug, otherwise these products should be applied in July.
  • Early summer is also when we start seeing turf diseases that are of a serious enough nature as to warrant the use of a fungicide.
  • Dollar spot begins to appear when temperatures are in the 60- to 80-degree Fahrenheit range, though symptoms can appear when it’s as hot as 95 degrees.
  • Conditions that also favor the disease include excessive moisture on the leaf (more than 10 hours per day), excess thatch, poor fertility and shade or poor air circulation. The symptoms on the leaf include an hourglass-shaped lesion with reddish/brown borders. You may also see cobweb-like hyphae over dew-moistened turf in the morning.

Hourglass-shaped lesions and cobweb-like hyphae are characteristic of dollar spot, along with silver dollarsize tan-brown patches in the turf. Several fungicides are registered for preventative and curative control.

Mid/late summer

  • Creeping bentgrass is a perennial grass that may be selectively controlled using three sequential applications (14 to 21 days apart; consult the label for specifics) of mesotrione beginning in mid-August. If overseeding these areas, the seed should go down on the same day as the third and last application of mesotrione.
  • Many of the most serious disease issues on athletic fields occur in the summer, associated with hot weather conditions. Gray leaf spot is a serious disease of perennial ryegrass and tall fescue turf and tends to occur most frequently in late summer. Conditions that favor it are periods of hot, rainy, humid weather. High nitrogen levels in addition to other stress, such as compaction or inappropriate herbicide usage, also tends to favor this disease. Symptoms include blighting of the leaf tissue and gray lesions with a brown border formed along the leaf margins.
  • Gray leaf spot is a more difficult disease to control and recommendations often include preventative applications. The fungicides thiophanate-methyl, azoxystrobin, trifloxystrobin, pyraclostrobin and DMI fungicides (such as metconazole, myclobutanil, propiconazole, tebuconazole, triadimefon or triticonazole) in combination with chlorothalonil are recommended. Resistance to fungicides has been reported so fungicides should be rotated.
  • Fungicide programs should be started in mid-July to early August. Of course, another strategy to deal with gray leaf spot is to plant either a resistant cultivar of perennial ryegrass, or to switch to Kentucky bluegrass.
  • Brown patch is another serious disease of ryegrass and tall fescue that’s favored by hot weather and high humidity. Characteristic signs of this disease include patches with a “smoke ring” visible at the outer edge in the early morning.
  • Pythium is another disease that occurs in hot, humid weather. Symptoms include circular spots of slimy plants that mat together. Cotton-like hyphae may also be visible in early morning. There are both preventative and curative fungicides for the control of brown patch and Pythium.

Autumn

  • If you didn’t apply a preventative grub control and are now having issues with white grubs, a curative insecticide choice includes trichlorfon. It’s an old, organophosphate insecticide and is one of the few choices to control existing grubs, though some research data shows that some of the newer insecticides have reasonable curative activity as well.
  • If you had problems with perennial broadleaf weeds during the year, and if they’re still present on the field, autumn continues to be the best time to control them with a postemergence herbicide – more of the herbicide trans-locates into the root system during the fall, resulting in more complete control of the below-ground structures that make the weed a perennial.
  • Fall is also an important time for fertilization, core aerification and overseeding.