Research Objective
To summarize existing weed survey information; to conduct a new series of general weed surveys in the Prairie provinces.
Weed surveys of annual crops have been regularly conducted in the Prairie Provinces since the 1970s.
The most recent series of Prairie Provincial weed surveys began with Saskatchewan in 2014/15, followed by Manitoba in 2016 and Alberta in 2017. As the surveys have been conducted using a similar methodology, it is possible to determine changes in weed populations through time and identify potential new and emerging weed problems. Weeds identified as increasing in abundance can be targeted for attention by various agencies involved in weed science. The trends identified by the weed surveys are important to the research, industry, and extension communities for developing weed management recommendations for producers that are essential components of sustainable farming
systems.
The new series of general surveys in annual crops started in Saskatchewan in 2019. The survey sites were allocated based on seeded acreage of crops of interest with eco districts (areas of similar soil, landscape, climate, and vegetation). Quarter sections were randomly selected, and owners were contacted for permission to complete the survey. In July or August, all weeds found in 20 quarter meter square quadrants placed in set pattern in each field were identified and counted. Weeds present at this time are expected to produce seed and contribute to next year’s seed bank. The Saskatchewan Weed Survey was completed in the summer of 2021, after a delay of a year due to COVID restrictions. Over the two years (2019 & 2021), a total of 2,277 fields of spring wheat, barley, durum, oat, canola, flax, mustard, soybean, lentil, pea, and chickpea were surveyed.
The dry conditions in Saskatchewan in 2021 influenced the weed communities present, having fewer weeds overall and favouring drought-tolerant species. Weather may cause temporary increases in weed species abundance but can also give insight into potential effects of climate change. Weeds that consistently increase between surveys are cause for greater concern. These species may be increasing in range and/or abundance due to changes in farming practices (e.g., reduced tillage, crop rotations) and/or the evolution and spread of herbicide resistance. Green foxtail remained the most abundant species in the 2019/21 survey, a position it has held since the surveys began in the 1970’s. Volunteer canola, lentil, and wheat have increased in abundance over time. Kochia has also increased likely due to favourable weather in 2021 and the spread of resistant biotypes. Other species steadily increasing included round-leaved mallow and black medick. Low cudweed, spiny annual sow-thistle, and false cleavers did not do as well in the dry conditions of 2021 but maintained relatively high abundances in comparison to earlier surveys.
A website is currently being developed to increase accessibility to weed survey data. The website will include data from each of the Prairie Weed Surveys starting in the 1970s.