Keep crabgrass under control

Keep it dense A healthy stand of turfgrass is the best defense against crabgrass. Otherwise, voids in the turf can lead to breakthroughs. (Photo: Bob Mann)

It’s crabgrass season, and while experts say preemergent products are typically the best bet, they’ve also shared a list of things to think about regarding crabgrass for summer and fall.

Eric Czernich, owner of Connecticut Valley Landscaping,
Chicopee, Mass.

• Understand your product labels and use the right product for the right stage. “Certain herbicides only work during certain tiller stages,” he says of the number of stems the weed produces during its growth. His company offers lawn care, maintenance, pest control, design/build and irrigation services to a 75 percent residential and 25 percent commercial clientele.
• Note problem spots. This way, Czernich says, you can modify treatments next season to mitigate crabgrass issues.
• Raise the mowing height. At 3 to 3.5 inches, your clients’ turf will help naturally shade out weeds and save on postemergent applications, he says.

Raising the mowing height to 3-3.5 inches will naturally shade out weeds, including crabgrass. (Photo: Bob Mann)

Eric Reasor, Ph.D., PBI-Gordon Southeast research scientist

• Grow healthy turf. “Implementing cultural practices (i.e., mowing, fertilization, irrigation and cultivation) will facilitate turfgrass competitiveness against crabgrass,” he says.
• Know your postemergent herbicides. “Postemergent herbicides are a great tool to control what crabgrass breaks through the preemergent herbicide,” he says. “Examples of these herbicides include fenoxaprop, fluazifop, pinoxaden and quinclorac. Postemergent herbicides are most effective at early crabgrass growth stages with the addition of a spray adjuvant.”
• Think about resistance management. “Using the same herbicide over and over will eventually lead to crabgrass resistance to that mode of action,” he says. “There isn’t a large selection of herbicide modes of action for crabgrass control.” This is where cultural practices and spot treating breakthroughs with postemergents come in handy.

Bob Mann, director of state and local government relations,
National Association of Landscape Professionals and former agronomist

• Best defense is a dense stand “Do our crabgrass controls work as advertised? You bet they do, but they are not magic bullets,” he says. “Herbicides must be used in conjunction with best management practices. A dense stand of vigorously growing turfgrass is the very best herbicide of all.” Removing too much leaf material by mowing too low exposes the soil to sunlight, thus increasing soil temperature and increasing crabgrass pressure.
• Your application pattern matters, a lot. Apply the right rate across the entire lawn. “Too often, applicators will ‘cheat the edges,’ which causes insufficient herbicide to be applied along the perimeter of the lawn where crabgrass pressure is the greatest,” he says.
• Early down, early gone. “‘Early down, early gone’ is wise advice from my favorite weed scientist,” he says about early herbicide applications. While crabgrass is believed to hit full germination at 1,700 growing degree days, Mann says the weed isn’t done germinating, with at least 10 percent of the weed still germinating into summer and early fall. “Depending upon where you are in the U.S., (1,700 growing degree days) could be well into July. One preemergent application in early spring might be the cause of midsummer breakthrough,” he says.

Dave Biegacki, Nufarm customer and brand manager for
turf and ornamentals

• Keep ‘em covered. “Crabgrass is very opportunistic, so any void in the turf becomes a prime area for crabgrass,” he says. Quinclorac is a good herbicide to control crabgrass during turfgrass establishment.
• Healthy turf. Think about cultural practices, such as proper fertilization, watering, good drainage and aeration, to keep crabgrass at bay, Biegacki says.
• Tank mix. “Topramezone or fenoxaprop are good postemergent choices,” he says. “It is important to include methylated seed oil or crop oil concentrate in the tank with topramezone. Be aware that topramezone causes goosegrass and crabgrass leaves to appear bleached for seven to 14 days after application before plants die.”