Researchers at Agriculture and Agri-Foods Canada are sharing the results of a recent study on just how prevalent kochia is in the prairies.

That also included stats on just how Glyphosate and Dicamba resistant the weed is, a fact that's been a pain point for many farmers.

Dr. Shaun Sharpe, one of the co-authors of the paper, details the methods behind the study.

"We did a survey of kochia, which is a problematic tumbleweed here on the prairie. We conducted this survey in 2019 and the survey was conducted post-harvest. So typically after the crops are harvested starting in about October. This survey, it's a randomized stratified survey, meaning we take samples based on how much agricultural production there is in a given eco-district, which is a way that they divide up the land based on its ecology." 

"We would drive around to different RMs and then drive around until we found kochia, typically on the roadside, collected it, took it back to the lab, and got the seeds out of that sample. Then over the next two years, up to about late 2022, we would screen it in the greenhouse for Glyphosate and Dicamba resistance and we would evaluate those screenings. We would do them in flats and we would aim to have about 70 plants per flat and then we would compare them to known standards of susceptible and resistant biotypes."

Sharpe says they found plenty of kochia on their trip and plenty more samples that ended up being herbicide resistant.

"It was very prevalent. We sampled 137 RMs that had kochia that tested positive for Glyphosate resistance and a smaller number, 87 RMs, that we were able to check for Dicamba resistance and when you take that, that's pretty much a wide swath. About 87% had at least one trace and it ranged across all of the areas."

As they tested through moist and mixed moist grassland, the study found that the plants were moving northward.

The severity of resistance was also a focus, with researchers finding plenty in their samples.

"It is increasing in its severity. With Glyphosate, there are more samples that are testing positive, and the degree to which those samples are showing. With the screening, we would screen the flat, and then the percent that is able to survive is kind of how we expressed how severe it is."

"There were quite a few samples with a high level of survival, which is about 61 to 100 per cent of them survive. So that was about 22 per cent (of the samples)," said Sharpe, "But with the Dicamba, the vast number of those samples had a very low level, between one and 20 per cent, were able to rise. So the degree that that's impacting them is a lot less, but it will grow as time goes on if there's no intervention through different chemical modes of action of herbicides."

Sharpe recommends a variety of intervention techniques both with and without chemicals.

"From a chemical perspective, incorporating multiple modes of action is important. Right now a lot of producers that I talked to are using Group 14 herbicides, especially the pre-emergence ones that are applied to the soil that controls kochia when it's just emerging. So that way you don't have to wait for it to emerge and then spray it, and they're having good luck with that. "

"Then using competitive crops, barley for example, is known to be quite competitive. So if you can incorporate that into areas where there is a lot of kochia and it can help keep down the amount of biomass and seed production that's able to happen with that weed and then diversification as well."