September 21, 2011
Getting crops planted in the spring can turn into a tense waiting game when Mother Nature doesn't cooperate. Cold, wet conditions that pushed planting dates to the limit in many areas in early 2011 left little time for preplant herbicide applications. Even under less extreme circumstances, there's no time to spare in the spring before planters start rolling.
That's why more growers are including fall herbicide applications in their weed-control programs. Along with greater spring flexibility, they say they are enjoying improved weed control with fall treatments that help halt the development of winter annuals and keep fields clean through planting.
Changing conditions mean more winter annual weeds
With hard-to-control weeds such as common chickweed, henbit, marestail, purple deadnettle, mustards, pennycress and others becoming a bigger problem each season, it's more important than ever to get fields off to a clean start. When heavy weed cover blankets spring fields, soils remain cool and wet longer, delaying tillage operations and planting. Some winter weeds also provide a haven for insects that attack emerging crops.
A variety of factors are behind this growing problem, including:
General warming of fall and winter temperatures that improves conditions for weed growth
Increased adoption of no- and minimum tillage practices, which provide more cover and protection for weeds
Movement from effective preplant and preemergence herbicides to glyphosate and other post emergence applications
Glyphosate and other herbicide programs with limited residual activity that doesn't impact germination of winter annuals after harvest.
Fall-applied herbicides where needed can be helpful solution
An effective way to prevent weeds from producing seeds in the spring is with burndown and residual herbicide applications in the fall. These treatments, which can usually be made any time after harvest until the ground freezes, give growers a head start on spring weed control.
Kyle Rose, who farms 4,000 acres of corn, soybeans and wheat with his father, Joe, in Iuka, Ill., has been using a fall herbicide program to help control marestail, waterhemp, fall panicum and other weeds in corn and soybeans for 10 years.
"Applying herbicide in the fall helps us achieve our goal of having a no- or minimum-tillage program," Rose notes. "Fall treatments help make sure our fields are clean in the spring so weed pressure is not one of our worries whenever we can start planting. Plus, having clean fields in the spring means not having to get a sprayer out in front of the planter before a field is in planting condition.
The economic benefits of a fall weed-control program speak for themselves, says Rose. "With diesel fuel running at nearly $4 per gallon, making two or three trips across the field before planting adds up. That's when a $15- to $18-per-acre application of Canopy EX herbicide makes a lot of sense."
Since a number of factors affect spring weed growth, the use of fall herbicides does not always eliminate the need for a spring burndown treatment. Other factors, including weed populations and planting schedules, also must be considered when determining an effective weed-control program.
Fewer weeds means an earlier start to planting for these farmers
For Illinois grower Mark Wankel, early-season weed control gives him the edge he's looking for each spring. "Making that herbicide treatment in the fall means there's one less job to do in the spring," says Mark Wankel, Petersburg, Ill. "Plus, weed coverage shades the ground, keeping it cool and wet longer. By eliminating that problem, you can plant corn a couple of days earlier." Wankel, who farms more than 5,000 acres of corn and soybeans, as well as seed wheat for Pioneer Hi-Bred, has used DuPont Basis herbicide for several years but switched from applying in the spring to combining a fall treatment with his strip-till program.
"In the fall we put down nitrogen strips with anhydrous; in spring we plant right on top of the strips," Wankel says. "Before we began applying the fall herbicide applications, winter annuals were coming up so thick we could barely find the strips in spring. Now, we put a postharvest application down in the fall and it does a good job of holding back winter annuals through planting time in the spring. Then we come back with a postemerge herbicide at the V3 to V4 stage of corn growth and continue the weed control where Basis leaves off. It's an effective weed control program."
The goal with this fall treatment is to stop weeds before they start
Flexibility with his weed-control program is also key for Gail Witt, who farms 7,000 acres with his brother and two nephews near Missouri Valley in western Iowa. "If you plan for a fall herbicide application and weather doesn't allow it, you still have a chance to make a spring application," Witt says. "But if you're counting on spring preplant application and weather keeps you from getting it done, you have no other choices."
Gail's nephew, Johnnie Witt, who handles the operation's herbicide applications, was able to apply a post-harvest treatment with Basis to about half of the Witts' harvested soybean fields last fall, which were expected to be planted to corn in 2011. The remaining fields were treated with a preplant herbicide this spring. When the corn was about 8 inches tall, he made a postemergence treatment with glyphosate and mesotrione or atrazine.
The fall herbicide treatments provided far better control than spring applications, he notes, in part because of the unseasonably cool weather this spring. "With the fall spray, none of the weeds had a chance to establish," says Johnnie Witt. "Marestail is our toughest weed challenge, and in the fields where we made a fall herbicide treatment, it was controlled. That's a huge advantage for us." He adds, "Fall herbicide applications give us a head start on control. With so many acres to treat, preplant applications can become almost overwhelming in the spring."
Learn more: Visit basis.dupont.com and canopyex.dupont.com for more information about the benefits of fall herbicide application. Always read and follow all label directions and precautions for use.
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