What is a challenge associated with using preemergence herbicides in turfgrass?

The correct answer highlights a critical aspect of how preemergence herbicides function. These herbicides work by forming a chemical barrier in the soil that prevents weed seeds from germinating. For this barrier to be effective, proper activation through water is essential. When preemergence herbicides are applied, they need to be either watered in shortly after application or must receive a sufficient amount of rainfall to dissolve the herbicide and allow it to integrate into the upper soil layer. This activation process is crucial, as it determines the herbicide's effectiveness in preventing weed growth.

If the herbicide is not watered in, it may remain on the soil surface where it can degrade or become less effective, ultimately reducing its ability to control weeds. Thus, understanding the need for adequate moisture is vital for anyone applying preemergence herbicides in turfgrass management.