By Alayna DeMartini | Ohio State University
COLUMBUS — As farmers prepare fields for planting, chances are they’ll meet up with dandelions. The weed is making a comeback in Ohio after decades of thinning out.
The resurgence of dandelions in Ohio has been occurring over the last couple of years, said Mark Loux, a weed specialist with Ohio State University College of Food, Agricultural and Environmental Sciences. Dandelions can create deep, strong roots, and they’re extremely adaptable to herbicides, making them tough to get rid of.
“It doesn’t matter which herbicide you use, you can’t just beat it over the head if you let it go for a few years,” Loux said.
For a gardener, dandelions and weeds in general are a nuisance. For a farmer, weeds can affect profits, reducing yields by competing with crops for water, nutrients, and sunlight.
The most troublesome weeds for Ohio farmers to control are marestail, waterhemp, Palmer amaranth, giant ragweed and common ragweed. They cost the most to eliminate, and some have changed to withstand weed killers that used to kill them.
“We only have tough weeds left, and they keep adapting,” Loux said.
If dandelions are allowed to grow for too long, even effective herbicides will kill only the small plants. The rest will survive, Loux said.
Clearing dandelions from a field typically requires applying a weed killer three times during the year–in spring, summer, and fall. The fall treatment is the most important. With the comeback of the dandelion and other winter annual weeds, applying a weed killer to a field in the fall, before harvest, is a wise move, Loux said. That will prevent farmers from facing fields dense with weeds come spring.
In spring, Midwest farmers typically apply weed killers first during late April or early May. But when extended rain is forecast, it can be better to apply them in early April, he said. That’s because the trend toward very wet springs delays any kind of field work. And if farmers wait until late April or the beginning of May, they risk running out of time to apply the herbicides before they plant, Loux said.
After seeds are in the ground, farmers should wait no longer than about four to six weeks before applying another round of weed killer, he said. Getting the weeds when they’re just a few inches tall will keep them from reducing crop yields.
Dicamba use
Among the herbicides farmers can use this year are those that contain the chemical dicamba. Last fall, the U.S. Environmental Protection Agency reapproved the use of weed killers with dicamba. That was despite lawsuits and complaints nationwide about dicamba drifting from the field where it was applied to areas beyond that, destroying crops along the way.
Dicamba can kill broadleaf weeds, as opposed to grasses, and can harm or kill any crop that’s not genetically modified to tolerate it.
The products XtendiMax, Engenia, and Tavium–all weed killers for soybean crop fields–can be applied only before June 30, according to the new rules the EPA passed last fall.
Training is required to use those products. Anyone who uses them should be aware of his or her insurance company’s policy if dicamba drifts and does damage, said Peggy Hall, an agricultural and resource law field specialist for Ohio State University Extension.
The risk of damage from drift is high for nearby specialty crops such as organics, produce, orchards and vineyards, Hall said. As a result, applicators should create the widest possible buffer between where they spray and the next field or property, she said.
“Farmers who use dicamba must follow the label restrictions precisely,” Hall said. “Failing to do so could lead to liability for damages caused.”
The 2021 guide for controlling weeds in Ohio, Indiana, and Illinois can be purchased here: go.osu.edu/controlyourweeds.
