Drive XLR8 Herbicide Crabgrass Killer is only a post emergent herbicide and will only kill actively growing weeds. To prevent new crabgrass from germinating, a pre-emergent needs to be applied when soil temperatures are around 55 degrees.
Dimension 2EW is one of the most successful pre-emergents for crabgrass prevention.
Click HERE to view How to Get Rid of Crabgrass Treatment Guide
Quinkill Max contains the same active ingredient in the same amount as Drive XLR8 and can be sold in CT. It is also labeled for crabgrass and other similar weeds.
We do have a post-emergent product that can be used in your lawn for clover. Depending on the type of fescue you have, this product can be used at the time of seeding. Drive XLR8 Herbicide is a very good product that is labeled for clover, as well as various other types of broadleaf weeds. It is safe for use in fescue as well. If you are overseeding with fine fescue, it is recommended that you use Drive XLR8 at least 7 days before seeding or 28 days after emergence of the new seed. If you are overseeding with tall fescue, Drive XLR8 can be used at any time. We do recommend using an MSO surfactant with this product as well. Please check the label with regards to this.
A pre-emergent can be used at the same time as a post emergent. Prodiamine 65 WDG is a very good option. It will prevent many broadleaf and grassy weeds from emerging. This should be done when the soil temperature reaches 55 degrees Fahrenheit. In southern states, individuals should be using this product in late February or early to mid March depending on the soil temperature.
We would also recommend checking out our Warm Season Lawn Schedule as well. This gives very good information on when to fertilize, use pre-emergents, etc. in your lawn.
We have an entire page on our site that contains crabgrass killing products that are selective, meaning they will kill crabgrass and other weeds, but not harm your grass. Here is a link to the section: http://www.domyownpestcontrol.com/post-emergents-c-188_478_494.html
The first product on the page, Drive XLR8, is our most popular.