Released April 17, 2008
MANHATTAN, Kan. - The second-best time to control dandelions in the Midwest doesn´t last long. It arrives during or just after spring´s first flush of cheerful yellow flowers.
"Purdue University researchers discovered that fact just a few years ago. The timing is critical, though. And, springtime herbicide applications can always be hazardous to other plants," said Ward Upham, horticulturist with Kansas State University Research and Extension.
Until recently, fall has been the only recommended time to control dandelions, other than by hand-digging, Upham said. It still is the No. 1 choice because late in the growing season is when the weed starts to focus its efforts on storing winter food in its large tap root.
"Now we have two options. But, at any other time, you´ll be wasting time and herbicide by burning off the top growth, yet leaving the plant-producing tap root in place," he said.
Choosing spring is riskier, though, he warned. All plant growth then is new, tender and especially vulnerable to damage. The season also brings warming temperatures and breezes.
Broadleaf herbicides contain volatile chemicals, Upham explained. So, warm weather helps the herbicides´ spray droplets turn into chemical- containing vapors. Then, even slight breezes can take the vapor to nearby plants. Wind can carry it to affect plants a long distance away.
"We hear reports about mysterious plant deformities every May," he said. "The indicator plants that usually are the first to show damage are the eastern redbud, tomato and grape."
The recommended herbicides are combination products that contain 2,4- D; MCPP; and dicamba. Example trade names include Trimec, Weed Out, Weed-B-Gon, and Weed Free Zone.
"If you only have a few dandelions, consider spot treatments, rather than a blanket application. If you have to use your sprayer, pick a calm day, to reduce the potential for drift," Upham advised.
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http://www.oznet.ksu.edu/news/
Contacts: Mary Lou Peter-Blecha, mlpeter@ksu.edu
