In a 2008 Syngenta survey, many growers and retailers commented on the difficulty of controlling common lambsquarters. Even though this hearty broadleaf is not officially resistant to glyphosate, experts believe it is only a matter of time before it joins the ranks of other glyphosate-resistant weeds like giant ragweed, common waterhemp and Palmer amaranth.
Why do we need to focus on this weed species? Even without showing signs of resistance to glyphosate, common lambsquarters is a competitive weed for row crops. Depending on it habitat, lambsquarters grow up to 6 feet tall. One university reports that a density of just two weeds per foot of row can reduce corn yield up to 11 percent. A density of 75 plants per square yard in a soybean field can reduce yield by 50 percent.
University researchers are carefully monitoring common lambsquarters populations due to the great amount of genetic diversity, its widespread geography and the tremendous amount of seed it produces. Until this point, university studies testing for glyphosate resistance have all been inconclusive. Implementing resistance management practices, for example those mentioned in Glyphosate-Resistant Lambsquarters Threat on the Horizon, can help manage lambsquarters before glyphosate resistance develops.
Multiple-resistance is another concern. Common lambsquarters is already resistant to ALS and PSII herbicides. What if lambsquarters developed resistance to glyphosate? If growers are already struggling to manage lambsquarters, glyphosate resistance will only worsen the situation by eliminating perhaps the most effective herbicide option we have.
University weed scientists report it is more cost effective to mange weeds now than it is to control glyphosate-resistant weeds down the road. Click on the links below to explore ways to diversify your weed management program and solutions to manage lambsquarters: