My high school FFA crops judging team won the state crops judging contest more than four decades ago. It was so long ago that the state contest was held at the Indiana State Fairgrounds, not at Purdue University where it is held today. When we took home the trophy to Whiteland High School, some of the weed plants we knew best were jimsonweed, cocklebur, redroot pigweed, and lambsquarters.
Today, young judgers I help coach struggle most with this set of weeds, particularly jimsonweed and common cocklebur. Of course, they're judging younger versions of cockleburs before they develop their tell-tale burs. But I have a theory as to why they have trouble identifying these weeds.
Most of these kids are 1 to 18 years old. By the time they were traipsing around their dads fields or neighbors fields, once-pesky weeds like big-leafed cocklebur and the purple-stemmed giant of a plant, jimsonweed, were well under control. Roundup had changed agriculture, and these two weds were no longer big culprits as they were in the early days of weed control, when I was helping my father grow soybeans, and learning about crops and weeds.
Students have trouble identifying weeds that they don't see. They still can identify Canada thistle, because unfortunately it was around in 1970 and is still a threat in central and southern Indiana today. They don't have any problems with Pennsylvania smartweed, because the plant with the smaller but distinctive leaves and pinkish, characteristic seed head is still an issue today. So are the foxtails, all three, giant, yellow and green, and other weeds such as johnsongrass. Not the enemy it once was before Roundup, it still grows along creek banks and roadsides, especially in parts of central and southern Indiana.
So the weeds that were a cinch to identify four decades ago because we saw and fought them most often are unfamiliar to students today. It's just one indication of the big weed shift that has occurred due to changes in herbicides, cultural practices and tillage methods over the past four decades in Indiana.