A preemergence herbicide is typically applied to:

• A. Foliage
• B. The soil
• C. Water surface
• D. Seeds

Answer: (B)

Preemergence means the herbicide is placed where weed seeds will germinate, so it can act as the seedling is just starting to grow. That’s why these products are applied to the soil or soil surface: the active chemical needs to be in the root zone as the weed begins to emerge, not on the plant’s leaves after it has grown. When moisture from rain or irrigation moves the product into the upper soil layer, it creates a chemical barrier that inhibits or stops the weed seedling from establishing. Applying a preemergence herbicide to foliage or to water surface wouldn’t protect crops because the weed’s growth is not yet controlled through contact with the plant tissues, and applying to seeds themselves isn’t the intended method for this mode of action.