News

Palmer amaranth-waterhemp cross spells trouble for soybean growers

Research documenting the crossing of Palmer amaranth and waterhemp means growers will have even more difficulty controlling herbicide-resistant weeds. 

Minnesota Soybean research director David Kee says researchers in Illinois, Missouri, Arkansas, Kentucky and Tennessee have identified the hybridization of Palmer amaranth and waterhemp.

Speaking to Brownfield at the MN Ag Expo in Mankato Thursday, he says that’s concerning because it likely shortens the time Palmer needs to adapt as it spreads north.

“It’s like bringing in a Minnesota dairy cow and a Texas dairy cow. Bring the Texas cow up here, it wants to freeze to death. Take the Minnesota cow down to Texas, breed her, bring her back up, and the calf comes up and evolves in the system.”

Kee predicts the new weed species will not be as aggressive as Palmer, but possibly more aggressive than waterhemp.

He says management shouldn’t change much.

“If you look at what they’re doing down south, it’s very similar to what we’re doing here. Start with a good, solid pre-emerge package. Follow that up somewhere between 21 and 28 days later with a post-emergent that has a residual. Then focus on getting canopy closure.”

Palmer amaranth has been confirmed in eight counties since first being discovered in Minnesota four years ago.