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.
Following the completion of the new Saskatchewan provincial weed survey in 2021, Manitoba was surveyed in 2022. The survey sites were allocated based on seeded acreage of crops of interest with ecodistiricts (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 metre 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. A total of 704 fields of canola, spring wheat, soybean, oat, corn, barley, field pea, pinto bean, and sunflower were surveyed in Manitoba in 2022.
The spring of 2022 was extremely wet in Manitoba, leading to delayed seeding; however, weed control was good resulting in the lowest median weed density and the highest percent of weed-free quadrants ever recorded in the Manitoba weed surveys. Green foxtail remained the most abundant species in the 2022 survey, a position it has held since the surveys began in the 1970’s. Wild buckwheat ranked second, as in the previous survey in 2016. Five other species have been ranked amongst the top 20 most abundant species in each survey: lamb’s-quarters, redroot pigweed, wild oats, Canada thistle and pale smartweed. Of these, both lamb’s-quarters and redroot pigweed were found at their highest relative abundance in 2022. Three species reached the top 20 for the first time in 2022; foxtail barley, golden dock and green pigweed. Foxtail barley had been increasing in abundance since 1997 while golden dock and green pigweed were not identified in the surveys until 2016. Canola, kochia, biennial wormwood, round-leaved mallow, wheat and yellow foxtail were also found at their highest relative abundance in 2022. Spiny annual sow thistle, broad-leaved plantain, dandelion, false cleavers and barnyard grass species have increased since the initial surveys but declined in 2022 in comparison to 2016. The 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.