A ______ herbicide only affects parts of the plant where spray droplets land.

• A. contact
• B. systemic
• C. pre-plant
• D. defoliant

Answer: (A)

A herbicide that acts only where spray droplets land is a contact herbicide. It doesn’t move through the plant’s vascular system, so its effects are confined to the tissues it directly contacts—usually the foliage and stems that were sprayed. Because it stays where it hits, thorough spray coverage is essential; any uncoated tissue can survive and the plant may regrow from parts not touched.

Contrast this with systemic herbicides, which move within the plant (via xylem and/or phloem) to affect distant tissues, so even parts not directly sprayed are damaged. The other terms describe timing or use rather than how the chemical moves inside the plant: a pre-plant herbicide is applied before planting, and a defoliant is a type of herbicide used to cause leaves to drop. Hence, the description fits a contact herbicide.