Waterhemp Resistance on the Rise
Published: Friday, August 28, 2026
Group 15 herbicides, bleaching herbicides and 2,4-D are all showing failure to control weeds across Indiana. That's according to Bryan Young, weed scientist and professor of botany at Purdue University, who was featured at a pesticide applicators recertification program in Millersburg last Tuesday.
"It's not just here in Indiana where we're seeing waterhemp resistance of bleaching herbicides increase. It's in Iowa, it's in Illinois, it's in Missouri, it's in Kentucky, it's in Michigan," he said. "So, we're seeing it all over. The only thing that is going to slow it up is if we stop using those herbicides or stop using them alone and use other effective herbicides with it."
Young said that resistance is being spotted in seed corn production.
"That's my No. 1 concern HPB (herbicide product bulletin) resistance moving forward," he said.
Young said this could affect both corn and soybean acres.
"When we find some populations of waterhemp that are less sensitive to dicamba or 2,4-D—you know, the really good herbicides—and you go to that site and look at the waterhemp and you spray different things, eventually, you find that the bleaching herbicides don't work as well," he said.
This shows an association between group 15 herbicides, bleaching herbicides and 2,4-D, where, if waterhemp resists one of them, farmers find failure in all three.
Looking ahead, Young encourages farmers to incorporate one new practice or herbicide for weed control in their fields. He said this will help elongate the efficacy of the herbicides they use and slow down weed resistance.
Rachel Cobb, a meteorologist at the National Weather Service in North Webster, told farmers to expect dry conditions over the Ohio Valley heading into the fall. This is due to a very strong El Nino that has settled in over the past few weeks.
Looking back at the crop season from May 19 through Aug. 17, Cobb reported above normal rainfall totaling nearly 15 inches in northern Indiana. Rainfall crossed the threshold of the 30-year average in mid-March.
Looking forward, Cobb encouraged farmers to keep their eyes to the sky.
"There is a 90% chance of a very strong event," she said, referencing the Relative Oceanic Nino Index. "Stronger Events can make certain weather and climates more likely."
She added that the winter should be warmer and drier than last year.
Also featured during the meeting was Adam Shanks, Purdue Extension, who discussed cover crop seeding with a drone demonstration. He encouraged farmers to hire a UAV specialist for a season if they are considering getting their drone license to test the efficacy of the equipment in their farm operation.
Shanks added that when applying seed with a drone, three things are critical: swath width, speed, and the outlet size and seed spinner. He encouraged farmers to fly over a test plot, complete with pans to catch and indicate where seed lands, before applying seed via a drone over a field. Speed, he said, plays a critical role in where seed lands. If a drone is going too fast, it will tilt forward, changing the trajectory of the seed. Finally, the seed spinner can throw products differently depending on its size.
Other things to consider before investing in a UAV include: the need for a UAV pilots license, exemption paperwork, insurance, the Category 11 exam for use of drones for herbicide, fungicide and seed applications.
"The best return is to have all three," Shanks said.
Drone applications also require a two-man team, with one person to fly the drone and another to watch the sky. Shanks added that farmers must also issue a notice of drone application to the Federal Aviation Administration before heading out to the fields.
The PARP regulatory topic was the use of the Bulletin2Live website in order to ensure compliance with the endangered species act. Marshall County Extension educator Brieanna Slonaker led farmers in an example and directed them to fill out the online forms, print them and save them for their records. Regulations will begin to be more heavily enforced heading into 2027.
Farmers with questions about regulations should contact the Indiana Office of the State Chemist.
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