Weed Watch: Lambsquarters

 

Lambsquarters

Lambsquarters is one of the first summer annuals to emerge in the spring, with approximately 25% of the plants emerging prior to any spring tillage or burndown herbicide application. Peak emergence is typically mid- to late-season, but lambsquarters can emerge throughout the growing season.1

 

Lambsquarters is one of the most prevalent weeds found in the U.S. Soybean Belt.1

 

Can reduce soybean yields up to 25% with less than one lambsquarters plant per foot of row.2

 

Young Plants

Cotyledons and seedling leaves have a mealy gray cast but turn green with age. Leaves alternate and are triangular, 1 � to 10 inches long.3

 

Mature Plants

Lambsquarters plants typically average around 3.5 feet but under the right conditions can grow to 6.5 feet.3,4

 

Seed Pain Points

One lambsquarters plant can produce up to 176,000 seeds, and one study found that 32% of seeds remained viable after 20 years.2

Because of its early emergence, lambsquarters can be one of the more difficult weeds to control in soybeans. It is critical to make sure weeds do not exceed the maximum height for postemergence weed control.2

Keys to Managing Lambsquarters1, 3, 4

  1. Rotate crops

    to diversify herbicide programs and weed control strategies.

  2. Start clean

    with a burndown herbicide or tillage.

  3. Apply a pre-emergence residual application,

    using a residual product within 2 weeks before planting or prior to crop emergence.

  4. Apply a postemergence application to target small weeds early,

    before weeds grow taller than 4 inches.

  5. Prevent Seed Production.

    If weeds escape, use tillage or physically remove them before plants produce seed.