URBANA, ILLINOIS (RFD NEWS) — Researchers at the University of Illinois are studying how herbicide chemistries behave when controlling weeds such as waterhemp.
Weed scientist Dr. Aaron Hager says triazine herbicides can be grouped by molecular structure, with some classified as symmetrical and others as asymmetrical. He says that distinction plays a role in how the products perform in the field.
“We use what’s called symmetrical, and we use asymmetrical. A symmetrical triazine means that the nitrogen atoms in the phenol ring of that molecule are symmetrically distributed around that ring,” Hager explains. “A very common example of a symmetrical triazine is atrazine. An asymmetrical triazine means that those nitrogen atoms are not symmetrically distributed around the ring. The most common example that we have of a non-symmetrical or asymmetrical triazine is metribuzin. So where are we going with this?”
Hager says the difference is important because most triazine-resistant waterhemp in the Midwest is not controlled by symmetrical products, but may respond to asymmetrical options.
“So again, our summary is that the PPO resistance is really limiting the residual activity that we can get from many of our soil-applied products in soybeans. Quite honestly, I think we are missing something with metribuzin,” He continued. “I think that still can give us an option. Is it going to last the entire season? No. Is it going to control every other species in the field? Metribuzin never did it before, so why do we think it will now? It never killed a velvetleaf or cocklebur that I know of. But, if Amaranthus is your target species, that might be something to think about.”
Hager says metribuzin may offer another option for controlling waterhemp, while noting performance can vary depending on target weeds and field conditions.
