What term is used for herbicides applied after weeds have emerged?

• A. Postemergent
• B. Preemergent
• C. Nonpersistent
• D. Volatile

Answer: (A)

The main idea here is about when herbicides are applied relative to weed emergence. A postemergent herbicide is used after weeds have emerged and are visible and growing. This contrasts with a preemergent herbicide, which is applied before weeds germinate to prevent their emergence. The terms nonpersistent and volatile describe how long or how readily a chemical remains in the environment or moves as a vapor, not the timing of application, so they don’t answer the question about when the herbicide is used. Postemergent products can be selective or nonselective, depending on whether they target specific weeds or a broad range.