I can't help you with a spray but I can help you prevent it in the first place. If you really need a spray, hopefully someone who uses herbicides will come along to help.

The best way to keep crabgrass out of the lawn is proper watering (deep and infrequent) and mowing it high (to shade out new weed seedlings). This is assuming you have good grass density.

For fescue, getting good grass density starts in the early fall time of year. If your grass is thin for whatever reason, fall is the time to seed new fescue. Why fall? Because crabgrass seed sprouts in the spring, not the fall. If you seed in the spring, you are also watering the crabgrass seed. Also fall seeding gives the grass roots plenty of time to harden off in preparation for summer heat. If you plant fescue seed in the spring, you will have to water it shallow and frequently which is exactly what crabgrass seed needs. And when the spring seeded grass dies out in July from the heat, the only thing left will be the crabgrass.

This time of year you should be watering once a month to keep the soil biology happy. As the temps warm up into the 70s, you can move to watering once every 3 weeks. With temps in the 80s, water every other week. When it gets to the 90s, go to once per week. If you have temps above 100 for a full week, then try going to every 5 days instead of every 7. The idea here is to put a lot of water down all at one time and allow the surface of the soil dry out completely before you water again. This damp/dry cycle practically guarantees that crabgrass will not sprout. Crabgrass needs continual moisture for a week to sprout. Sometimes Mother Nature is responsible for making that happen, but you don't have to help Her along.

First, I know this sounds silly, make sure that your yard is predominantly a perennial turf grass. People ask me all the time what pre emergent herbicide they should use in their yard and come to find out that their yard is 75 percent crabgrass. There is not much use in applying a pre emergent if you don't a somewhat decent stand of turfgrass. Dimension (active ingredient dithiopyr) pre emergent herbicide gives you the widest margin for error. Dimension has some post emergent activity on crabgrass, so if you miss your application window by a week it will kill any crabgrass that has already germinated. Barricade (active ingredient prodiamine) is also a very good pre emergent herbicide. Barricade does not have any post emergent activity but it does have a longer residual than dimension. Remember that no pre emergent herbicide is going to stop all weeds. The two herbicides I just mentioned are the best pre emergents for turf, but they work best on grassy weeds so you will most likely have to clean up some broad leaf weeds and any nutsedge with post emergent herbicide sprays. Timing of the application of your pre emergent herbicide is the most critical step of the process. Buy a digital thermometer that you can insert in the soil. Start measuring the soil temp. (maybe the end of March, maybe earlier depends where you live in NC) and when the soil temp. at one inch depth reads 55 or above for a couple of days in a row then apply the herbicide. Then, after applying the product water in the application with half an inch of irrigation. Also, make sure you read the label carefully and apply enough herbicide to last at least into the month of September. However, if you have a yard with cool season turf then you will want the product to have ceased activity sometime in September if you need to do any reseeding.