What can happen if liquid preemergence herbicides are applied to tall grass and mowing occurs soon after?

What can happen if liquid preemergence herbicides are applied to tall grass and mowing occurs soon after?

• A. The herbicide becomes more effective
• B. The herbicide may not reach the soil surface in effective amounts
• C. It improves blade safety
• D. It enhances weed control of mature plants

Answer: (B)

Preemergence herbicides must be in the soil, at the surface where weed seeds will germinate, to form an effective barrier that prevents those seeds from sprouting. When a liquid product is applied to tall grass, it mainly sits on the leaf surfaces rather than the soil. Mowing soon after can remove or significantly reduce that surface residue and prevent the chemical from reaching the soil in the amounts needed. Without enough herbicide in the soil, the germination barrier isn’t established, and weed control is reduced or lost. The other outcomes don’t fit how preemergence products work: they don’t become more effective on foliage, they don’t improve blade safety, and they don’t target mature plants.

Preemergence herbicides must be in the soil, at the surface where weed seeds will germinate, to form an effective barrier that prevents those seeds from sprouting. When a liquid product is applied to tall grass, it mainly sits on the leaf surfaces rather than the soil. Mowing soon after can remove or significantly reduce that surface residue and prevent the chemical from reaching the soil in the amounts needed. Without enough herbicide in the soil, the germination barrier isn’t established, and weed control is reduced or lost. The other outcomes don’t fit how preemergence products work: they don’t become more effective on foliage, they don’t improve blade safety, and they don’t target mature plants.