Texas FFA Nursery Landscape Practice Exam

When should a pre-emergence herbicide be applied?

1. To broadleaf weeds only

2. After the weeds have emerged

3. To grasses only

4. Before the weed seeds germinate

The correct answer is: Before the weed seeds germinate

A pre-emergence herbicide is designed to be applied before the weed seeds germinate, which is why the answer is correct. The primary purpose of this type of herbicide is to create a chemical barrier in the soil that targets weed seeds as they begin to germinate, preventing them from growing into established plants. This type of herbicide is effective against a broad range of weeds and is typically used in the early spring or before the planting of crops and ornamental plants. The other options describe situations that are not effective for applying pre-emergence herbicides. For instance, applying herbicide to already emerged weeds or targeting only specific types (like broadleaf or grasses) does not align with the purpose of pre-emergent use, which is preventive in nature, aiming to stop the development of weeds before they even begin to sprout.