All the way to mid-November is typically a great time to knock out dandelion, says Bryan Overstreet, a Purdue University Extension educator in Jasper County. He is also an Indiana Certified Crops Adviser.
The only catch to fall dandelion control is that the plants still need to be green.
"If you're going to plant soybeans next year a combo of Canopy and 2,4-D is very effective," he says. "If you're going to plant corn in 2016 in the field where you have dandelions a Basis and 2,4-D combo is your best bet."
What if you don't know what will be in the field next year? Maybe you want to maintain flexibility or spray the same mixture on a number of fields with differing rotations.
"A combo of glyphosate and 2,4-D is a very good option in that case," Overstreet says. He recommends that to get exact rates for the products, consult the labels for each herbicide that you intend to use.
You can also consult the Illinois, Indiana and Ohio 2015 Weed Control Guide published by the three land-grant universities in those states for more specific details.
Danny Greene, owner of Greene Ag Consulting, LLC, Franklin, and also a CCA, emphasizes how important timing of applications can be in controlling dandelions.
Purdue publications suggest that the most effective application is after a frost, not before. However, Greene has seen good control when applications are made on dandelions anytime from early October to mid-November, as Overstreet also noted. And as he noted, the important thing is that the dandelions are still green and active, he says.
Dandelions are tough to knock out with one application. That's why you need to do as many things right as you can, including timing the application and picking the best products available for your situation, to have a good shot of getting full control and knocking them out, the agronomists agree.