When glyphosate-resistant waterhemp was first discovered in Lambton County in 2014, University of Guelph weed scientist Peter Sikkema never imagined the course the weed would take across Ontario, or the speed it would travel.
Fast forward to 2022 and glyphosate-resistant waterhemp has moved 700 kilometres east to Leeds & Grenville County. The invading resistant weed, often misidentified as redroot, green, or smooth pigweed, has now been found in 14 counties across the province. In eight of the counties, four-way resistance has been confirmed, making the weeds resistant to Group 2, 5, 9 and 14 herbicides.
In soybeans, Sikkema’s research reveals that the average yield impact of waterhemp is 43 per cent, but he has documented losses of up to 100 per cent in the most competitive environments. For corn, the average loss is 19 per cent, but as in soybeans, losses can reach up to 100 per cent.
Based on his research, Sikkema recommends Ontario farmers employ a two-pass weed control program to control the herbicide-resistant weed. “Whether you are growing corn or soybeans your strategy should be similar,” he says. “In both crops, start with your best soil-applied herbicide and then manage the weed escapes with a post-emergent herbicide.”
During the 2021 season of virtual Ontario Diagnostic Days, RealAgriculture’s Bernard Tobin joined Sikkema for a tour of his glyphosate-resistant waterhemp research plots. Check out the following video report for Sikkema’s top product recommendations to control the weed in corn and soybeans.