What is a critical guideline for using pre emergence herbicides?

Using pre-emergence herbicides requires careful timing and application to be effective, particularly in relation to laying sod. The first option emphasizes that these herbicides should not be applied before laying sod unless specifically indicated. This guideline is crucial because pre-emergence herbicides function by inhibiting seed germination of weeds. Applying them before laying new sod could prevent the sod’s own roots and seedlings from establishing properly, thereby hindering the growth of the desired grass.

Additionally, pre-emergence herbicides are formulated to create a protective layer in the soil that targets weed seeds as they germinate. If this layer is applied incorrectly, it can harm the new grass or prevent it from rooting effectively. Therefore, adhering to this critical guideline ensures both the success of the sod installation and maximizes the herbicide's effectiveness in controlling weeds once the sod is established.