Grainswest - Fall 2025

Fall 2025 Grains West 42 “If we know where the weeds are headed, we can intervene by supporting agronomists, extension specialists and farmers in those areas.” —Shaun Sharpe the two methods delivered results. Tidemann recommends the two- punch combination to farmers battling herbicide-resistant wild oats. She also noted little difference between straight cutting and swathing, although the latter tended to mildly increase efficacy. “Every farm requires a unique weed management strategy,” said Tidemann. Employing early maturing crops such as spring barley or winter wheat may not work for everyone, but her research may inform new approaches or inspire on-farm, out-of-the-box thinking. “Leveraging HWSC, like weed seed collection or impact mills is another perspective for combating problem weeds that works, too. It isn’t a static control measure—it can be adopted to fit on individual farms.” PIGWEED RISK Shaun Sharpe is determined to limit the march of two scary weeds into Western Canada. “The greatest potential threat to Prairie farmers is Palmer amaranth and waterhemp,” said Sharpe, an AAFC research scientist. “Both weeds are wreaking havoc across the U.S., and Eastern Canada has dealt with waterhemp for years. What’s most alarming is they are very prolific and resistant to multiple herbicide groups.” Amaranths, also known as pigweed species, are common in Canada. Of 14 established species, nine are herbicide resistant. Waterhemp has invaded Manitoba and is expected to creep across the Prairies. Most waterhemp in Canada is resistant to at least one herbicide mode of action, with multiple resistances common. Palmer amaranth remains a looming threat, with a few plants identified in Ontario and Manitoba. One of the most competitive amaranth species, it is resistant to multiple herbicide modes of action. Sharpe worries about the potential economic impact of these weeds and limited control options. In response, he now leads a four-year research project that aims to reduce the risk posed by the two weeds and help farmers manage them if they do take root. Both species are known to dramatically increase yield loss and input cost as well as reduce harvest efficiency and grain quality. In Ontario alone, herbicide-resistant waterhemp has caused an average yield loss of 19 per cent in corn and 43 per cent in soybeans. On farms with extremely high waterhemp pressure, yield loss can be up to 99 per cent in corn and 93 per cent in soybeans. A 2001 study of a Kansas corn field reported a yield loss of 91 per cent due to Palmer amaranth. BIOVIGILANCE IN ACTION Sharpe predicts Palmer amaranth will reach Saskatchewan between 2030 and 2035 if it hasn’t yet done so unnoticed. Waterhemp will likely spread at a similar pace. Both weed species can produce up to one million seeds per plant and spread easily via contaminated feed mixes, irrigation water and dirty equipment. They are also transported naturally by wind and wildlife. Sharpe and his team employ biovigilance. This multi-pronged, holistic approach includes monitoring the spread of pigweed species in Western Canada, raising awareness about their impact and development of new tools to help the industry identify and manage these weeds. The work is supported by the analysis of existing research and the experience of other geographic regions, tracking herbicide resistance trends and identifying effective management strategies. The project kicked off in April 2025 with the development of a weed identification process. Weed images collected and studied by the project team will support the creation of a plant ID app. Farmers and agronomists will use it to identify the weeds, but Sharpe wants to take this one step further by making genetic tissue sample testing available. He now oversees the development of a system to handle samples. These activities will support development of a predictive niche mapping tool expected to identify areas at risk for weed invasion. “If we know where the weeds are headed, we can intervene by supporting agronomists, extension specialists and farmers in those areas,” said Sharpe. “We want to be ready to help them identify the weeds, manage their risk and deal with the weeds if necessary.” Field trials were also carried out this year in Saskatoon, SK. Using grain amaranth as a pseudo weed, Sharpe evaluated the effectiveness of cultural control strategies across multiple crops. Industry awareness is the overarching component of the project. An associated extension campaign began with tours of the grain amaranth demo plot at Ag in Motion, this July in Langham, SK. “These weeds are a serious threat, and, if established, it would be like battling kochia all over again,” said Sharpe. Every acre is at risk of amaranth invasion, he added. “Everyone needs to be on the lookout, because they can spread so easily.” Farmers should be on the lookout for these weeds and prepare to engage all necessary weed control measures. FEATURE