How Long After Spraying MSMA Can I Seed?

Weed Control with MSMA

• MSMA is one of the three main arsenical herbicides used in the United States since the 1950s, making it one of the oldest used herbicides. It is used for postemergent weeds and works by inhibiting plant growth through a loss of chlorophyll. MSMA is primarily used for the control of numerous annual grassy weeds in turf sites. The chemical is also used for weed management in cotton, citrus and industrial and noncrop areas.

Seeding After MSMA

• In order to minimize damage to newly seeded lawn sites, apply no chemical products, including MSMA, to the site for at least a month prior to seeding, cites the University of Missouri Extension. The control of weeds with either mechanical methods or with the use of herbicides is important before planting seed to reduce competition for the newly emerging grass seedlings.

Herbicide After Seeding

• Experts also recommend waiting a certain period of time after seeding to start the use of postemergent weed management strategies like MSMA. If used too early, the chemicals will kill the new grass along with the weeds. The general rule of thumb is to avoid the use of chemicals until the new lawn is mowed three or more times, suggests David R. Mellor in "Picture Perfect."

Herbicide Use Suggestions

• Controlling annual grassy weeds is usually very difficult after germination. MSMA and CMA are the only main herbicides that are considered efficient postemergence control for annual grassy weeds. MSMA is commonly sold as crabgrass killer in liquid form and comes under different trade names. Grassy weeds die very gradually and require repeat applications. Avoid using MSMA at more than the recommended rates as it can damage the turf. Discoloration in grass after MSMA use is only temporary.