Differentiate between preemergence and postemergence herbicides and give one example of each used in turf.

• A. Preemergence targets emerged weeds; example: prodiamine
• B. Postemergence targets weed seed germination; example: quinclorac
• C. Preemergence targets emerged weeds; example: quinclorac
• D. Preemergence targets weed seed germination; postemergence targets emerged weeds; examples: prodiamine; quinclorac

Answer: (D)

Timing differentiates preemergence from postemergence herbicides. Preemergence is used before weed seeds have germinated, forming a soil barrier that prevents those seeds from emerging. Postemergence is applied after weeds have already emerged, aiming to kill the actively growing plants. In turf, prodiamine is a classic preemergent that prevents germination of crabgrass and other annual grasses, while quinclorac is a common postemergent used to control emerged crabgrass and similar weeds. This pairing matches both the weed stage targeted and the typical turf applications, which is why it’s the best answer.