As weeds increase in resistance, try cover crops, specialist says

KEMPTVILLE — Weeds are increasingly resistant to the current suite of herbicides used in agriculture, but there are alternative techniques to bolster the dwindling chemical arsenal.

“The reality is, I’ve been around for 22 years, and there are no new herbicides coming into the marketplace that I know of,” OMAFRA weed management specialist Mike Cowbrough told farmers who gathered to hear his weed control advice on Jan. 16 at the Eastern Ontario Crop Conference. “We’re seeing more herbicide resistance, so we just need to utilize other things to try and take the pressure off those herbicides.”

Cover crops, a focus on ensuring efficient canopy closure, a shift to pre-emergence herbicides, and a new weed-zapping technology are all part of the mix. Cowbrough’s advice pertained mostly to weed control in soybeans and corn.

Cowbrough highlighted the benefits of cereal cover crops — especially cereal rye — planted and harvested in advance of soybeans. All cereals exude natural alleopathic chemicals that inhibit weeds, but cereal rye puts off the most, he said. “It’s pretty easy to manage, it’s not overly expensive, it’s pretty easy to kill, and it’s also the one that’s been most researched,” he added.

That said, farmers need to manage their expectations about cereal rye as a weed management tool because the crop has a beneficial impact only about two thirds of the time, according to Cowbrough. Canada fleabane is particularly susceptible. “Aside from herbicide, only cereal rye consistently reduces the amount of population of Canada fleabane,” he said.

While drone-applied herbicide is currently illegal, he pointed out that drones can be used to broadcast cereal rye seed into standing corn.