Tips for Especially Troublesome Weeds

The lower dose of 2 ounces of aminopyralid for Canada thistle seems to knock them out while not visually impacting common milkweed that may be within or close proximity to the thistle patch. Here in Black Hawk County we have found several problem weeds and brush. This year we started to use aminopyralid, triclopyr, metsulfuron-methyl for our brush and broadleaf herbicide, and we also have several spots of Japanese knotweed that we sprayed with triclopyr and completely killed. We sprayed it early to mid-summer and only a handful of small re-growth occurred. Then we also sprayed the regrowth, and it’s now dead. 
—Griffin Cabalka, Black Hawk County, 2024

Consider hitting teasel rosettes again in the fall after the main spraying is done because you just don’t have time to hit everything during the season. Rosettes can be missed and you can go back in the fall in bad areas and hit what you missed and get ahead for the next growing season.
—Josh Batterson, Wapello County, 2024

With spring burns for multiple years in a row up to four years with follow-up mowing and spot spraying, we saw a huge reduction, close to 90 percent, in wild parsnip in a native plot we manage using this technique.

Mow or cut Japanese knotweed mid-summer, then apply aminopyralid in the fall right before the first frost. 

To manage phragmites, use a strong solution of glyphosate mid-summer with yearly follow-up and re-treat.

For leafy spurge, use two applications of potassium salt of aminocyclopyrachlor at least two weeks aparat in the spring and a fall application if possible.
—Lakota Kirst,  Cerro Gordo County, 2024

Aminopyralid achieves a very high level of control on thistle with minimal disturbance to grass. A custom mix for spraying cut stump, cut stubble, and basal is better than premixed stuff.
—Wes Gibbs, Jones County, 2024