Which statement describes a limitation of contact herbicides?

Which statement describes a limitation of contact herbicides?

• A. They kill both above ground and below ground parts.
• B. They do not kill the underground parts of the plant.
• C. They are systemic and translocate to roots.
• D. They provide long-term residual control in soil.

Answer: (B)

Contact herbicides work by damaging plant tissue that is directly touched; they do not move systemically through the plant. Because they stay where they contact, their effect is limited to the above-ground parts that are touched, and they do not reach underground tissues such as roots, rhizomes, or tubers. That limitation means they may not completely kill plants that persist through underground structures, and regrowth from underground organs can occur after treatment. As a result, they’re best for quick burn-down of accessible foliage or for use on annual weeds, often requiring thorough coverage or follow-up applications. The other statements describe properties that aren’t characteristic of contact herbicides: they are not systemic and do not reliably provide long-term soil residual control.

Contact herbicides work by damaging plant tissue that is directly touched; they do not move systemically through the plant. Because they stay where they contact, their effect is limited to the above-ground parts that are touched, and they do not reach underground tissues such as roots, rhizomes, or tubers. That limitation means they may not completely kill plants that persist through underground structures, and regrowth from underground organs can occur after treatment. As a result, they’re best for quick burn-down of accessible foliage or for use on annual weeds, often requiring thorough coverage or follow-up applications. The other statements describe properties that aren’t characteristic of contact herbicides: they are not systemic and do not reliably provide long-term soil residual control.