Soybean South


Pre-emergence Herbicide
Protects Investment

Missouri farmer says pre-emergence herbicide – a new combination of two active
ingredients – does a good job on large-seeded broadleaf weeds like cocklebur
and giant ragweed.


In West Alton, Mo., David Bonderer sees a return to using pre-emergence herbicides in soybeans. He sees it on his 2,500-acre farm, as well as on his neighbors’ operations, which he services through his family’s dealership, Saale Farm and Grain.

“Many growers will apply a pre-emergence on early beans,” Bonderer says. “It holds weeds down, and maybe lets us plant a little earlier. Controlling those weeds also helps us in terms of insect control. And it’s going to buy us some time to make that glyphosate application a little closer to canopy so we can get by with just one [application].

“You’re going to spend the money one way or another,” Bonderer notes. “Glyphosate will cost you $4 per acre plus the application cost, so you’re looking at $8 for a second glyphosate or $12 for a pre-emerge. So a pre-emerge is going to be a little more expensive, but hopefully you’ll plant your beans a little sooner and you’ll be going into a clean seedbed.”

Bonderer tried Prefix last year, a new combination of S-metolachlor (the active ingredient in Dual Magnum) and fomesafen (the active ingredient in Reflex). He says a stale-seedbed combination of Prefix and Touchdown did a better job on large-seeded broadleaf weeds like cocklebur and giant ragweed than other pre-emergence herbicides he’s used.

“And we got better grass control than most,” he adds. A single postemergence application of Touchdown took Bond-erer’s beans, planted on 15-inch spacing, through canopy and into harvest.

Waterhemp worries
Bryan Young, an Illinois weed scientist, adds that glyphosate isn’t a sure bet for controlling some key broadleaf weeds, which increases the level of competition all season long. “With broadleaf weeds in particular, we’ve been getting inconsistent results with glyphosate – weeds like lambsquarters, giant ragweed and morningglory,” he says. “If those weeds get too much height, glyphosate becomes inconsistent.”

Like most weed scientists, and many farmers, Young is concerned about glyphosate-resistant waterhemp. He advocates the use of at least two modes of action on waterhemp populations. Young says Prefix shows strong promise in the fight against glyphosate-resistant waterhemp.

“Prefix is one of the few herbicides that combines two different modes of action for waterhemp in one product,” he notes. “Both S-metolachlor and fomesafen have significant amounts of waterhemp activity. With the two modes of action in Canopy XL, sulfentrazone did all the waterhemp control there – it was never the ALS herbicide. In Gangster and Gauntlet, they both contain one waterhemp herbicide with another herbicide for small-seeded broadleaf weeds.”

“In most cases, we’ll be following Prefix with an application of glyphosate,” Young points out. “Three modes of action for waterhemp control in any given year is a pretty good effort.”

‘Not the weed-killing industry’
“If growers think of herbicide as a cost, they’d probably be hesitant to change what they’re doing,” notes Young. “But if they think of herbicide as an investment, they see that it’s worthwhile to apply a pre-emergence treatment.

“It’s called the crop protection industry, not the weed-killing industry,” he points out. “We’re not using these products to kill weeds; we’re using them to protect our investment. That should dictate the timing and choice of the herbicide.”

By that model, a pre-emergence herbicide is a wise approach indeed.

Gibbs and Soell, who represents Syngenta, provided information for this article.