Pre-emergent herbicide
Turf
In plain English
Pre-emergents are applied in early spring (and again in fall in some regions) to prevent crabgrass, goosegrass, and other annual weeds. Timing is critical — too early and it breaks down before the weeds germinate; too late and the seeds have already sprouted.
Why it matters for lawn care operators
Pre-emergent application typically requires state pesticide certification. If your business is mowing-only, this is a service to refer out, not perform yourself.