The best way to control weeds such as crabgrass and other summer annual weeds is with a pre-emergent herbicide applied in early spring. This needs to happen before crabgrass seeds germinate, which typically begins in late March here in Oklahoma and on into April, May, and June. So as long as the pre-emergent is applied before then and watered into the soil, crabgrass should not even germinate.
There are differences in pre-emergent products, and there can be big differences in how and when those products are applied, that will greatly effect the results. At LawnAmerica we use the very best product available, Barricade or prodiamine, which is the chemical name. We apply this between now and mid-March for our existing customers, at the rate of 29 oz. per acre, which will provide about 6-7 months of good crabgrass control according to the chart above. Our 6 and 7-step customers also receive another 8 oz. of prodiamine with their Round 3 Echelon treatment applied during the May to early June time period, which extends the control of crabgrass and other weeds even longer into the summer. Other pre-emergent products are more water soluble, and may not hold up to heavy rains as we experienced last year. Barricade did.
Other lawn care companies in Oklahoma tend to apply a lesser rate of products, and apply them in what they call a “split application”, with some applied in their step 1, and more in their step 2. So, their customers are paying twice, for what LawnAmerica does in ONE treatment. So much for their lawn care being “cheaper”. As long as Barricade is applied by an experienced and good technician, at the proper time, and with the proper rates, one treatment will suffice. And, if a booster rate is applied deeper into spring as we do after that first flush of crabgrass germination, then all the better results will be obtained.
Any pre-emergent needs to be watered into the soil also in order to be activated, so we’ll need help either from Mother Nature or from an irrigation system, which may be you with a water hose! The newer pre-emergents such as Barricade do not break down in the soil or leach out of the soil nearly as fast as older products that I was using years ago, so that’s good. The biggest factor is still how and when they are applied as to why one lawn looks great, and another may have a crabgrass problem.