Let's say you have a field that looks like the one pictured here and you haven't sprayed it yet. As my four-year-old grandson, Graham, says, "Pa, those are beautiful yellow flowers."
I don't agree with him, even in the yard. In the field at least in dry springs, Bill Johnson, Purdue University Extension weed control specialist, has seen them choke out a stand of corn.
Your best option is to spray glyphosate and 2,4-D plus something with Classic's active ingredient in it, such as Canopy or another Canopy product, Johnson says. The problem comes if you're hoping to no-till soybeans into this field, and you have to spray the whole field for dandelions.
Depending upon the rate you apply of 2,4-D, labels require you to wait seven to 30 days to avoid plant injury. Those recommendations ahead of soybeans are pretty solid, he says.
What if you don't want to wait? You can apply without 2,4-D, but don't expect much more than a knock-down on the dandelions, Johnson says. "They're really easier to kill in the fall, so you're up against a tough fight anyway," he notes. "If you take the 2,4-D out you're going to lose a lot of killing power against them at this time of year."
Suppose you're coming back with corn after corn. You still need the 2,4-D in the mixture, Johnson says. However, most labels on 2,4-D products word the caution about spraying seven days before or after planting corn more loosely, he says. That doesn't mean you couldn't end up with a situation where you damage the crop by not waiting long enough to plant, or be spraying 2,4-D too soon after planting and before emergence.
You can control patches, which often appear in fields, but you still need to follow the same label recommendations if you spray patches of dandelions as if you spray the entire field, Johnson says.
For farmers to maximize soybean yields, they need to maximize their management. Often soybean management takes a backseat to corn, but it doesn't have to. Download our free report, Boost Your Soybean Yield, for a one-stop look at ways you can better manage your crop.