Preemergent herbicides should be applied when to control summer annual weeds?

Preemergent herbicides should be applied when to control summer annual weeds?

• A. Late spring
• B. Late summer or early fall
• C. Any time weed seeds germinate
• D. Late winter or early spring

Answer: (D)

Preemergent herbicides must be present in the soil before weed seeds begin to germinate, forming a barrier that prevents seedling emergence. For summer annual weeds, germination typically starts as soil warms in spring. Placing the herbicide in late winter or early spring positions it ahead of that germination window, so the chemical is active when seeds try to sprout. If you wait until late spring, many seeds have already germinated, and the barrier won’t stop them. Late summer or early fall comes after the germination window for summer annuals, so it’s not effective for controlling them.

Preemergent herbicides must be present in the soil before weed seeds begin to germinate, forming a barrier that prevents seedling emergence. For summer annual weeds, germination typically starts as soil warms in spring. Placing the herbicide in late winter or early spring positions it ahead of that germination window, so the chemical is active when seeds try to sprout. If you wait until late spring, many seeds have already germinated, and the barrier won’t stop them. Late summer or early fall comes after the germination window for summer annuals, so it’s not effective for controlling them.