After the quiet months of winter, warming temperatures and longer days often mean a mad dash to get the season started. Prioritizing weed management early is critical to reducing yield loss and future risks.
“Over the years, I’ve determined the burndown period is the most critical of the season,” said Monty Parish, a farmer in Henderson, Kentucky. “You only have one chance to kill winter weeds before you plant your crop.”
Sprayer Prep
The perfect application conditions are often hard to come by. When temperatures rise and the sun starts to shine, have equipment ready to go to minimize downtime.
Flush the sprayer of antifreeze products, and check the system for leaks and wear. Wesley Everman, an Iowa State University Extension weed specialist, recommends removing boom end caps to check for residue.
“Some products can have a clay base that leaves a residue that accumulates at the end of the booms,” he said. “As we get into the new season, we don’t want [old chemicals to contaminate] anything we’re spraying.”
Double-check that nozzles match recommendations for chosen chemicals and have favorable spray patterns.
“In the spring, coverage is huge,” said Drake Copeland, a technical service manager for FMC. “If a grower made a later application [last year], they may have switched to a nozzle that is unfavorable for burndown applications.”
Be sure to calibrate gallons-per-acre settings before entering the field. While it may be tempting to cut down on water usage, Copeland said resisting that urge can lead to better spray coverage and more successful weed control.
Have a Plan
If looking to plant early, consider which fields should be sprayed first.
“The fields you want to plant first, that is where you definitely want to have a handle on any winter annuals that have gotten out of control,” Copeland said.
Prioritizing applications in problem fields, such as those that lay wet, can also allow for better control before spring rains come.
Be aware of crop plans and plant-back intervals, especially when using a formula with a residual sense, double-check that chosen chemicals are meant for present weeds to prevent costly mistakes.
“Keep it simple,” Copeland said. “There’s a lot of options out there, but go with what you know works and select the appropriate adjuvant.”
When to Spray
Parish, the Kentucky farmer, utilizes spring burndown for winter annual control on his corn-and- soybean operation. Ground conditions and air temperature are his main concerns when determining when to enter the fields.
“I want my air temperature to be a bare minimum of 40°F, and it’s helpful if the sun is shining,” he said.
Weeds must be actively growing for herbicides to bind to the site of action and provide effective control. When looking at the forecast, aim to apply when temperatures are closer
to 50°F for two to three consecutive days to ensure cold fronts or low nighttime temperatures don’t shut down weed growth.
Courtesy of FMC
Measuring Success
Measuring the success of burndown applications is largely visual.
“It’s an almost instant gratification,” Parish said. “Within a few days, you know if the program has worked, because the weeds are either dead, or they aren’t.”
Some spring burndown applications work slower than those in summer, when plants are going through rapid growth. In general, farmers can expect to see results within 10 days.
Dead weeds are not the only benefit of effectively controlling winter annuals; clean fields hold less moisture and allow for earlier planting. There’s also less risk of insect and nematode problems later in the season, since many winter annuals serve as hosts for those pests.
When the timing is right, Parish maximizes his burndown application by adding a residual product, eliminating the need for an additional pass across the field at planting.
Is It Necessary?
Despite busy schedules and mounting input costs, early-season weed control is not the place to cut corners. Timely control of herbicide-resistant weed species, such as marestail, in particular can drastically limit issues later in the year.
For fields with less tricky weed species, tillage or cover crops may be viable options for suppression. Failing to control winter annual weeds can have devastating effects, with some species reducing yields by up to 50%.
“It’s a message we’ve heard for years, but starting clean and staying clean is more critical than ever,” FMC’s Copeland said. “If there’s money to be spent on herbicides, the way you start the year is where you’ll see the best return on investment.”