The most common and effective crabgrass pre-emergent herbicides are Prodiamine (Barricade), Dithiopyr (Dimension), and Pendimethalin (Halts). For this article, we will continue to focus on the most popular Group 3 herbicides: Prodiamine and Dithiopyr. Both crabgrass preventers are considered Root & Shoot Inhibitors.

To prevent crabgrass from germinating in your lawn, apply a pre-emergent early spring because this is the time when the weed will start to sprout in your lawn. The University of Arizona says to apply pre-emergents when the temperature is high enough for the seed to take water but before any germination.