Diquat is used to control which type of aquatic vegetation?

• A. Algae control and terrestrial weeds
• B. Submerged aquatic macrophytes and algae
• C. Floating leaf and submerged aquatic macrophytes and algae
• D. Emergent plants

Answer: (C)

Diquat is a contact aquatic herbicide, meaning it kills plant tissue on contact rather than moving inside the plant. Because it acts where it touches, it can rapidly knock down vegetation that sits on the water surface (floating-leaf plants), as well as submerged aquatic macrophytes and even algae that come into contact with treated water. This broad action is why it’s used to control multiple types of aquatic growth quickly, so the best choice includes floating-leaf vegetation, submerged aquatic macrophytes, and algae. Other options restrict the target to terrestrial weeds, submerged plants and algae only, or emergent plants, which doesn’t capture the full range diquat can affect.