2025 weeds stealing yields include pigweed, lamb’s quarters, grasses, velvet leaf, and ragweed.
As the growing season winds down, now is an ideal time for Ontario farmers to assess the effectiveness of their weed control strategies and prepare for the next growing year.
Dr. Holly Byker, Agronomy Manager at the Ontario Crop Research Centre in Winchester, emphasizes the importance of scouting fields to identify weeds that escaped control throughout the season. Common offenders in Ontario in 2025 include pigweed, lamb’s quarters, grasses, velvet leaf, and ragweed.
Byker notes that environmental conditions, such as rainfall patterns and temperature fluctuations, play a significant role in herbicide performance.
For example, herbicides applied just before rainfall often achieve excellent control, while dry spells may limit effectiveness.
Timing is also critical, especially in no-till systems where crop emergence and canopy closure influence weed pressure.
Understanding which herbicides were used, and why they may have been less effective, helps farmers make informed decisions for the next planting season.
Resistant species, such as water hemp and Canada fleabane, require careful attention. Testing samples through programs that identify genetic resistance can provide insight into which herbicides remain effective, allowing for strategic planning.
Integrated approaches beyond herbicides are also important. Adjusting row spacing, for instance, can improve canopy coverage and limit light reaching the soil, helping to suppress weed emergence. Early-season control is particularly critical, as weeds established early can multiply quickly, producing seed banks that persist for years.
Byker highlights the value of hands-on learning and field observation. Identifying weeds in person, rather than relying solely on photos or apps, builds confidence and familiarity with varying biotypes and appearances caused by genetic variation and cross-pollination.
For example, distinguishing between green and red-root pigweed or recognizing the smooth, waxy stems of water hemp is easier with direct observation.
Successful weed management involves careful reflection on past practices, understanding the biology and resistance of target species, and planning pro-active strategies for the next growing season.
This article was created based on a presentation by Dr Byker during the Great Ontario Yield Tour event in Osgoode, Ontario, watch the video below.