A name like lambsquarters may conjure images of cute baby animals or children’s nursery rhymes, but, as farmers know, this weed is a wolf in sheep’s clothing. The summer annual can be difficult to control and can rob corn yield if you’re not careful.
According to the Michigan State University Extension, lambsquarters can cause up to 13% yield loss in corn. This substantial loss can occur with as little as one weed per 1.5 feet of row.1
Lambsquarters is so competitive because it grows quickly and produces a lot of seeds. Mature plants can reach up to 5 feet tall and produce, on average, about 72,500 seeds. Those seeds are also particularly hardy. It can take up to 12 years to deplete the seedbed by 50% and up to 78 years to deplete it by 99%.1
Lambsquarters can be devastating, so it’s important to know what to look for in your cornfields. When the plants are seedlings, they feature two lance-shaped cotyledons.
As they mature, the weeds develop triangle-shaped leaves with toothed margins and a white, grainy surface. Adult lambsquarters have smooth stems that can appear green to reddish in color. You can also watch for small gray-green flowers that grow in clusters on the stems.
Lambsquarters is one of the earliest-emerging summer annual weeds. About 25% of the plants emerge prior to spring burndown applications or tillage. Peak emergence occurs in mid- to late-spring with seeding typically in late summer into fall.2
Lambsquarters can be difficult to control, because it has developed resistance to two herbicide groups: ALS inhibitors (Group 2) and photosystem II inhibitors (Group 5). The first resistant populations were found in the 1970s.2 Today, 22 states have lambsquarters with some sort of registered herbicide resistance.
At this point, the weed is not registered as resistant to glyphosate in any U.S. state. However, some populations are less sensitive to the ingredient than others.
When it comes to controlling lambsquarters, the earlier you start, the better. There are not a lot of postemergence options available to control it. So, you’ll want to use a full program approach with burndown, preemergence and postemergence herbicides.
In corn, you can use Realm® Q herbicide as a burndown, followed by a preemergence application of SureStart® II herbicide and then a postemergence application of Resicore® herbicide. All these options contain multiple modes of action and residual activity to control lambsquarters throughout the season and manage resistance.
Those aren’t the only options though. There are several solutions from Corteva Agriscience to fit your farm. You also can try cultural practices like tillage, rotary hoeing and crop rotation to suppress lambsquarters.
As mentioned before, this weed emerges early, so be on the lookout for it this spring and take steps to keep it under control. It sounds like something cute and cuddly, but it will take a bite out of your yield if you let it.
1Michigan State University. Common Lambsquarters. https://www.canr.msu.edu/weeds/extension/common-lambsquarters
2United Soybean Board. 2021. Common Lambsquarters. https://iwilltakeaction.com/weed/common-lambsquarters
Realm® Q, Resicore® and SureStart® II are not registered for sale or use in all states. Resicore and SureStart II are not available for sale, distribution or use in Nassau and Suffolk counties in the state of New York. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions.