Which statement about preemergence and postemergence herbicides is true?

Which statement about preemergence and postemergence herbicides is true?

• A. Postemergence herbicides are applied to soil before germination
• B. Postemergence herbicides are applied to emerged weeds
• C. Preemergence herbicides are absorbed by the leaves
• D. Preemergence herbicides kill established plants

Answer: (B)

Postemergence herbicides are applied after the weeds have emerged, targeting actively growing tissue on visible weeds. That timing is why this statement is true: you apply postemergence products to emerged weeds to kill or suppress them. In contrast, preemergence herbicides are applied to the soil before germination to prevent weed seedlings from establishing, so they don’t rely on leaf uptake. Saying preemergence products are absorbed by the leaves is inaccurate because their primary action is through the soil and on germinating seeds. Also, preemergence herbicides are not meant to kill established plants; they are used to prevent emergence, not to control plants that are already growing.

Postemergence herbicides are applied after the weeds have emerged, targeting actively growing tissue on visible weeds. That timing is why this statement is true: you apply postemergence products to emerged weeds to kill or suppress them. In contrast, preemergence herbicides are applied to the soil before germination to prevent weed seedlings from establishing, so they don’t rely on leaf uptake. Saying preemergence products are absorbed by the leaves is inaccurate because their primary action is through the soil and on germinating seeds. Also, preemergence herbicides are not meant to kill established plants; they are used to prevent emergence, not to control plants that are already growing.