Fall Burndown Helps Manage Weed Threat After Long Growing Season

Fall burndown applications help manage weed threats.
Strategic fall burndown applications help manage weed threats into spring.


New fall burndown strategies for weed control can help bring weed threats under control.

This year’s mild winter and early spring led to a fast start to fieldwork. In many parts of the country, growers started planting crops two to three weeks ahead of normal. That led to a longer growing season – for both crops and weeds.

Weeds got an early start in 2012, thanks to unusually warm temperatures in February and March. “For many growers, that meant weeds were bigger than usual before preplant herbicide applications were made,” says Helen Flanigan, product development manager, DuPont Crop Protection. “Spring control was especially difficult where no herbicide had been applied the fall before. Those fields definitely needed to be managed more quickly in the spring, which wasn’t always possible.”

As this growing season comes to a close, there is also greater potential for weed growth after harvest, says Flanigan. “If much of the crop is harvested earlier than normal, and fall weather stays mild, weeds that germinated later in the season could mature enough to produce more seed, adding to the weed seed bank.”

A post harvest herbicide application could be an excellent weed-control strategy this fall and for next spring, she adds. “Residual herbicide activity would help control late-season weeds to reduce potential seed production, manage early winter annuals and provide control into spring.”

Growers who are experiencing increasingly complex weed situations are finding that planning strategic residual herbicide passes, such as a fall application of DuPont™ Canopy® EX herbicide followed by a spring application of DuPont™ Envive® herbicide on soybeans, provides the reliable weed control often necessary for managing herbicide-resistant waterhemp, giant ragweed and marestail, reports Bruce Knoernschild, account manager, DuPont Crop Protection. A phased approach helps prevent resistant weeds from becoming a serious problem, plus the grower benefits from better planting and crop establishment conditions, improving yield opportunity.

“In Missouri, the growers I work with have found that a fall herbicide application is an important initial step for managing resistant waterhemp and giant ragweed,” says Knoernschild. “In wet spring weather, not having a mat of winter annual weeds allows the field to dry faster. When the spring is dry, reducing the weed population means soil moisture is available for the young crop.”

Fall application helps prepare for spring uncertainties

Last fall, Ron and Ben Miller, who farm near Towanda, Ill., applied DuPont™ Basis® Blend herbicide to soybean fields going to corn and Canopy® EX to their corn acres going into soybeans. Ron reports the timing couldn’t have been better. “With the mild winter and early spring, we saw winter annual weeds go to town in other fields, but ours were clean this spring.

“We typically have problems with henbit, but had virtually no winter annuals come up this spring,” he explains. “We didn’t have to use our normal burndown application and the residual weed control lasted through planting. Then, when conditions turned dry in June, we made just one postemergence pass in both corn and soybeans.”

This year, being able to eliminate a spring herbicide application represented significant savings in both time and money, Ron Miller notes. “Herbicide for a burndown pass would have cost $20 to $22 per acre, so the $8- to $9-per-acre cost of our fall application was a very cost-effective option.”

Over the past few years, the father-and-son team has gradually increased the number of acres on which they’ve made post harvest herbicide applications. “It is a good fit for our operation, which includes no-till soybeans and strip-till corn,” he says.

In recent years, wet springs have made it difficult to get into fields early to apply burndown treatments, Miller says. “That is one reason we moved to more fall-applied herbicide. We often have more time in the late fall. Last year, because it stayed warm until Christmas, we had plenty of time to get all our acres covered at the end of November.

“We rented some new land at the end of 2011, with no access until December, but we were able to make a herbicide application there, as well. Since we didn’t know exactly what weed spectrum we were dealing with on new land, the Basis® Blend application seemed like good insurance.”

Weed control critical for no-till acres

Nathan Deppe says the farming operation near Washington, Mo., he runs with his father and uncle has moved to a mostly no-till operation to reduce compaction. Increasing fuel costs, better corn hybrids and planters that can effectively place seed in no-till conditions also played a role in their decision.

Developing an effective weed-control strategy has been an essential part of increasing no-till acres, he says. “A fall-applied herbicide application of Basis® Blend on soybean acres going into corn helps with any late-season marestail, as well as being effective on winter annuals, including henbit and chickweed. We’ve also found that with a fall-applied herbicide, there’s less weed mat to plant through the next spring. That also means soils warm up faster.

“I don’t like to have any weeds in our corn fields ‑ even a few weeds reduce yields ‑ so we work hard to keep our fields clean,” Deppe adds. “That’s why we follow a corn-soybean rotation as much as we can. Rotation is an important part of reducing weed pressure because it gives us more flexibility in herbicide use.”

He says fall-applied Basis® Blend has provided good weed control until early May. “This year we were able to start planting corn in mid-March, so that kind of control really helped get the crop off to a good start.”

2012 Update: Dry Conditions Give Weeds a Boost

Early-season growing conditions were good in many parts of the Corn Belt in 2012, but dry conditions across the midsection of the country in early summer reduced effectiveness of some postemergence herbicides. Because of that, weed control this season was only fair for many growers, says Helen Flanigan, product development manager for corn and soybean herbicides for DuPont Crop Protection.

“Poor weed control wasn’t due to lack of effort,” she says. “Most growers were making what would normally be timely postemergence applications in June. But by July, there were weeds visible in fields above the soybean canopy, and it was obvious that there were some weed escapes,” she notes.

“It’s likely the cuticle on those weeds had already thickened in the dry conditions, so not as much herbicide was taken up,” she says. “After harvest this fall, I expect we’ll see more of those escapes in the field.”

If this year’s harvest is early, weeds will have more time to grow in the fall, says Flanigan. “I’m telling growers who see more weeds than usual after harvest to not ignore them. Those fields will benefit from a post harvest herbicide application.”

For soybean acres going into corn next season, DuPont™ Basis® Blend herbicide provides effective fall burndown with residual control that lasts into spring. On corn acres that will be planted to soybeans next spring, DuPont™ Canopy® EX herbicide offers powerful burndown post harvest, with residual control to keep fields weed-free until planting.

Post Harvest Weed Control Delivers Big Benefits

Controlling late-season weeds is just one reason many growers are taking advantage of a post harvest herbicide applications. Other benefits include the following:

  • Reliable weed control. Combining a fall burndown treatment for late-season emerged weeds with a spring residual herbicide application provides weed control through planting.
  • Streamlined workload. Many growers can reduce hours of spring work by moving a preplant spring herbicide pass to after harvest.
  • Cleaner spring fields. Controlling winter annuals before they get established means fields are ready to plant as soon as weather conditions permit.
  • Warmer soils for planting. Earlier weed control can reduce the mat of dead weeds that often remains after a spring burndown. That speeds soil warming and dryout, especially in no-till fields.
  • Faster crop growth. A warmer, drier seedbed means more uniform emergence and better seedling vigor.
  • Less insect pressure. Fewer weeds in the field mean insects have less habitat for populations to become established.

DuPont™ Basis® Blend and Canopy® EX may not be registered for sale or use in all states. See your DuPont retailer or representative for details and availability in your state.
Always read and follow all label directions and precautions for use.