Under what condition is diquat considered a restricted-use product?

• A. When product contains less than 18% diquat.
• B. When used in a public water supply watershed.
• C. When product contains more than 18% diquat.
• D. When used near submerged aquatic vegetation.

Answer: (C)

Diquat’s status as a restricted-use product is determined by how strong the formulation is. When a diquat product contains more than 18% diquat, it is designated as restricted-use because higher concentrations carry greater risk to people and the environment, so applications must be performed by a certified applicator and follow stricter labeling and handling requirements. If the product is 18% or less, it is not restricted-use, though you still must follow all label directions and safety precautions. Other restrictions, like not applying in a public water supply watershed or near certain aquatic vegetation, matter for where or how you can apply the product, but they don’t define whether the product is restricted-use—the concentration does.