Weeds Make a Comeback in Southern Minnesota

This is a bean field I drive by every time I go out to the farm. I do not even know whose field of beans it is, but it definitely has an issue with giant ragweed. Giant ragweed and tall waterhemp have become two problem weeds in our area. I remember growing up a sign of a "good" farmer was a weed-free bean field. Farmers walked their beans and pulled tall waterhemp, pigweed, button weeds, lambsquarter, smartweed and other weeds. That meant it took a lot of time and work.

Then in 1996 Roundup-ready beans were introduced and it was easy to control all weeds. Beans could tolerate Roundup and all the weeds were killed. Over time we saw some weed species shifts. Some weeds emerged later on in the season after the last application of Roundup. Other weeds like waterhemp and giant ragweed developed a tolerance or resistance to Roundup. Today it takes a soil-applied herbicide before bean emergence and at least one, maybe two, post-emergence herbicide applications. We are back to where we were when I was growing up. A sign of a good farmer is the ability to control weeds and have a "clean" bean field.