Avoid the nasty complex

Strategic green and tee complexes attract rounds, revenue, members, and favorable reviews. Too many unsightly weed complexes detract from the otherwise positive and pleasant aspects of a golf course.

With summer entering its back nine, here’s a refresher on the steps necessary to avoid an abundance of broadleaf weed complexes emerging in fairways and rough.

Broadleaf weeds develop in bunches

If you spot one type of broadleaf weed on your course in July or August, other types are likely in the same area, according to PBI-Gordon Southeast research scientist Dr. Eric Reasor. Doveweed, Virginia buttonweed, spurge, prostrate knotweed and lespedeza are among the weeds that thrive in hot weather.

“It’s rarely one thing all over the place,” Reasor says. “It’s usually a hodgepodge type of thing. We want to control those weeds before they start producing seed because that will go into the soil and make more weeds for next year. Ideally, if you’re waiting until mid-summer or August, you probably need to be targeting weeds before then, when they are younger and more immature and more susceptible to herbicides.”

Weeds like thin turf

We’ll get to herbicide use and selection. Before we reach that point, it’s important to understand where broadleaf weeds emerge. Thin turf might add roll to drives and approach shots, but it also expedites potential summer weed growth. Multiple broadleaf weeds seek gaps and weaknesses in the turf canopy.

Dispersing cart traffic, reducing shade, avoiding mower scalping, and providing proper irrigation and nitrogen fertility are tactics Reasor recommends for limiting summer weed issues before they arise. “If you have any thin areas of turf that aren’t just as quite healthy as you would like them, these weeds are going to find their place in any type of opening,” he says.

More about doveweed

Doveweed has become more prevalent on golf courses over the past decade, according to Reasor, who is based in north Texas and covers a territory spanning from Florida to West Virginia. Doveweed struggles handling cart traffic; bare patches are a negative consequence associated with its emergence.

A member of the spiderwort family, doveweed tolerates low-mowing heights and can resemble common turf species such as St. Augustinegrass and centipedegrass. Doveweed is a monocot (most broadleaf weed are dicots) and has a grassier appearance than other summer broadleaf weeds. The grassy appearance masks a control fundamental.

“It’s controlled like a broadleaf, although it behaves a little more like a grass,” Reasor says. “Once you get to herbicide selection, broadleaf weed herbicides control doveweed.”

Herbicide selection

Promised we’d discuss herbicides. The conversation has a logical starting point.

“No. 1, know your turf,” Reasor says. “If you have bentgrass or a cool-season hodgepodge, with fescue, bluegrass, ryegrass and maybe some bentgrass, make sure you know your turf and how much injury you can tolerate.”

Once a superintendent knows what his or her turf and clientele can handle, their senses must be operating at high levels.

“Scouting is important,” Reasor adds. “I have been on this soapbox for several years now. We are just waiting too late in the year to spray these broadleaf weeds. We’re waiting until they are so noticeable that we have to spray them.

“For the most part, we know where these things have occurred in the past, we know they are a problem, year after year. So, let’s get out there earlier, let’s scout for small seedlings and immature weeds, and apply these herbicides earlier rather than later. It doesn’t matter what herbicide you use; it’s going to work better on a younger plant than an older, mature plant.”

Beware of the heat

Numerous active ingredients in broadleaf herbicides, including popular synthetic auxins 2-4D, dicamba and MCPP, can’t be used in all summer situations.

“They’re in tons of products and most of the time there are temperature restrictions,” Reasor says. “Usually, it’s around 85 to 90 degrees Fahrenheit. There are two reasons why. One, it can increase injury to turfgrass. Two, if you apply at temperatures above that, we can lose that herbicide to volatility. With the heat, that herbicide will actually turn to a gas and it can move with the wind to areas where we don’t want them.”

And watch for rain

Rain is another weather condition to avoid when applying herbicides to control summer broadleaf weeds.

“You don’t want to water them in,” Reasor says. “We want that herbicide to stay on the leaf surface as long as possible. There are rainfast times. With certain herbicides, you can get a rain within a couple of hours and it’s fine. But for most herbicides, by and large, we want that herbicide to be on the leaf surface.”

Reasor adds that using an adjuvant or surfactant with an herbicide can boost effectiveness. “If you think of spurge, it has real tiny leaves. If we can put a surfactant in there to help an herbicide stick to those small leaves, that will help with control.”

Think of combinations

Herbicides featuring multiple active ingredients are helping superintendents in warm- and cool-season environments control weed complexes. PBI Gordon’s Q4 Plus, for example, combines quinclorac with 2,4-D, dicamba and sulfentrazone. Q4 Plus is labeled to control more than 80 broadleaf and grassy weeds on warm- and cool-season turf.

“There’s a lot of different weeds out there and not every weed is going to respond to the same herbicides,” Reasor says. “A combination like Q4 Plus is going to attack that spectrum of weeds with multiple modes of action. You’re not going to just have broadleaf weeds. We can take one product and control a lot of different weeds.”

Going after the big one

Crabgrass remains a staple of weed complexes encountered on golf courses and it can become a late-summer issue even if treated with a preemergence herbicide. “Pre’s work very well,” Reasor says, “but they’re not 100 percent effective.”

Quinclorac is a common active ingredient in postemergence herbicides labeled for crabgrass control and using those products effectively requires understanding the weed’s growth stages.

“The biggest thing with crabgrass postemergence is don’t wait until it’s super mature,” Reasor says. “A lot of these products, like quinclorac, work great early and they work good very late. But there’s a time period of growth stages where that plant is just so actively growing that a lot of herbicides aren’t as effective during that time. Apply early in the season if you know you’re going to have breakthroughs. And then using a surfactant really helps with quinclorac.”

One postemergence application might not be enough to handle the gnarliest crabgrass. “I would plan on multiple applications, especially if you didn’t put out any pre’s,” Reasor adds.