What is a preemergence herbicide?

• A. A chemical used after weeds emerge.
• B. A fertilizer.
• C. Pesticide applied to seeds after germination.
• D. A chemical applied to control weeds before their emergence from the soil.

Answer: (D)

Preemergence herbicides are chemicals applied to the soil before weed seeds germinate to prevent them from emerging. They act as a barrier in the topsoil, inhibiting or killing seedlings as soon as they try to grow, and they often need rainfall or irrigation to activate and reach the germinating seeds. Timing is key because these products don’t affect weeds once they’ve emerged. This contrasts with postemergence herbicides, which are used after weeds are visible, fertilizers which supply nutrients, and seed treatments that apply chemicals after germination.