The Upper hand in Smutgrass Control

When cattle producers and forage experts in the southeastern United States talk about the toughest pasture weeds to control, smutgrass is always near the top of the list.

According to Brent Sellers, you can find smutgrass in almost any pasture in southern Florida. “Smutgrass always ranks in the top three toughest weeds in the survey of county and state extension staff that we conduct every five years,” says the University of Florida extension weed specialist. The weed is also prevalent in Alabama, Georgia, Louisiana, Mississippi and Texas.

Smutgrass is aggressive, doesn’t need much moisture and produces seeds from May through the summer months throughout the Southeast. “And mowing smutgrass can actually increase its seed production, so mechanical control is not a good option,” notes Sellers.

In pastures, smutgrass spreads and competes with desirable perennial grasses, says Randy Verret, location manager for G&H Seed Co., Iowa, La. “As smutgrass invades, it occupies more area in the pasture and eventually reduces carrying capacity. Animals overgraze the desirable, more palatable grasses, which gives smutgrass even more opportunity to spread.”

Early control option

The key to effective control is taking action before weed density is too great, notes Sellers. “Once smutgrass covers more than 50 percent of the pasture, it’s often too late for spot-spraying. When an infestation gets up to 60 or 70 percent, you’re looking at pasture renovation.”

That can be a costly proposition, says Sweet Lake, La., ranch manager Jason Tate.  A few years ago, Tate worked with his retailer Verret to try a herbicide control approach for smutgrass on bermudagrass. Verret recommended using DuPont™ Velpar^® L herbicide. “We had a high infestation of smutgrass and were looking at tearing up the pasture. But the Velpar^® L application worked well,” says Tate.

In March 2011, grazing restrictions for Velpar^® L were significantly reduced. Now pastures treated with Velpar^® L at 4.5 pints per acre or less can be grazed immediately and treated acres may be cut, dried and fed 38 days after application.

Best time to apply

For best smutgrass control, apply Velpar^® L when weeds are actively growing, advises Craig Alford, range, pasture and invasives portfolio manager for DuPont Crop Protection. “For many areas in the Southeast, that’s in May and June, when rain is more frequent.”

In central and southern Florida, July and August have proven to be good application months, says Sellers. “But really it’s less about the specific month and more about when it rains more frequently. It’s best to time an application between rains or the day before rain is expected, since that timing seems to encourage maximum root uptake.”

It’s important to adjust the application rate of the herbicide based on soil texture, notes Alford. He adds that, while the herbicide is one of a grower’s limited options for controlling smutgrass, Velpar^® L also controls nine other weed species, including barnyardgrass, dogfennel, fescue, lespedeza and pigweed.

Sellers encourages fertilization after herbicide treatment. “Adding nutrients will increase forage production and allow the bahiagrass or bermudagrass to quickly fill in the open areas created by dying smutgrass.”

According to Verret, who has worked with growers for many years to control smutgrass, the new label change for Velpar^® L is a significant opportunity for better pasture management. “Eliminating the grazing restriction lets cattle producers treat infested areas before smutgrass spreads, without having to give up a whole pasture.”