Southern Spotlight: Superweeds, Herbicides, and You

James Banahan

James Banahan

Weeds are crazy things.  A single marestail plant produces 250,000 seeds per season.  A single pigweed plant costs your operation $22 a day in lost inputs.  And you can give a waterhemp plant a bath in Roundup without it suffering so much as a yellow spot.

If they weren’t so lousy destructive and costly to our industry, I might say that weeds are pretty impressive things.

But destructive and costly they are.  And the alarming ease with which they thrive makes it seem that we can barely blink in our combat against them.  For these reasons, agronomists at UFC and other co-ops around the area have been advocating fall burndowns for weed control.  Now, you either did or did not follow such advice at the end of last season.  If you did, then good for you.  You’re a step ahead with weed control, but the info here is still essential knowledge for you.  If you didn’t, then this article is especially for you: not only is the info essential, but there are yet actions you can take to get a handle on weeds this season.

Perhaps you’ve heard talk of “superweeds” over the past year or so.  What we’re generally referring to when we talk about superweeds are weeds that have developed a resistance to Roundup, which, as you well know, has been our go-to herbicide for nearly two decades now.

Roundup has never been a silver bullet in our fight against weeds.  As I’ve mentioned already, it doesn’t cure waterhemp, nor does it cure problems with marestail or giant ragweed.

As the evolution of superweeds elongates the list of weeds that Roundup doesn’t kill though, it is becoming increasingly imperative that we add modes of action to our weed control planning.  Different groups of chemicals affect plants in different ways, which means that weeds that don’t respond to Roundup’s particular mode of action may still respond to a different chemical that will act on the weed in a different way.

Take, for example, the reproductively proficient marestail.  It is unaffected by Roundup but 2-4 D and dicamba (which you likely know as Banvel) kill marestail with relative ease.

There is no weed for which we don’t have some sort of solution, but don’t relax too much, because in bad cases, that solution is only partial and can be pricey.  Prevention of weeds remains the best practice possible.  A good prevention program costs between $25-30 per acre and wins you 80-90% weed control.  A rescue treatment on the other hand will cost you an additional $15 per acre and will achieve only about 40% control (we hope).


As you explore weed control options this spring, it is also of the utmost importance that you plan and understand how different herbicides will affect your crop plans.  2-4 D has an important role to play in our industry, but anyone using it must be mindful that soybeans can’t be planted for 5-7 days after its application.  If you’re exploring new herbicide options this season, be sure to explore their residual times and the limitations you might experience on future cropping plans.

Ultimately, it’s not too late to address your weed issues, but growing resistance to Roundup will likely find you wading into new territory with herbicides.  We’re quickly approaching the time to finalize your herbicide decisions, but don’t make your choices in haste.  Use your head and gather your info as you incorporate new products so that you understand how they will affect your plans and operation.