Tenacity (mesotrione) can be used as a pre-emergent. This is especially useful during seeding time. Most other pre-emergents will also prevent the grass seed from germinating but this will not.
To apply tenacity as a pre-emergent you want to blanket spray the whole lawn and then water in the application. It needs to reach the soil to work as a pre-emergent. If you don’t water it in you’re essentially using it as a post-emergent.
It should be noted that tenacity only lasts a few weeks in the soil, and it’s not the best pre-emergent. So I only recommend it for seeding time because something is better than nothing. Once the lawn has established I recommend using a traditional pre-emergent like prodiamine.
Related products: Tenacity
Related ingredients: Mesotrione