Where do you live? In most places in the northern hemisphere crabgrass is finishing the sprouting phase and concentrating on the seeding stage. And then in a few weeks it will all be dead anyway.

dchall is correct. Apply Halts anytime late winter until sod reaches 70 degrees. As far as I know, that's the only window.

As far as spraying it, why would you want to do that? Going to be inhaling a lot of chemicals. The granular stuff is pretty solid, very little dust blows around. Maybe zero dust, probably part of the design.

May want to look into this product and use a colorant to help avoid over spraying and or skips. If I remember right one five pound container should treat 4 acres.

http://www.domyownpestcontrol.com/prodiamine-65-wdg-generic-barricade-p-2495.html

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Prodiamine (Barricade) is very effective but be careful because it has a long residual - approximately 6 months or so if applied correctly, and can interfere with overseeding plans if applied in spring. Dimension is another good option and lasts approximately 3 months. Halts (Pendimethalin) works reasonably well but is a bit too short lived. It kept the crabgrass at bay in Spring but I've had a major breakout this summer. I'm sure all the rain this summer probably didn't help and might have washed away the barrier.

Edit - Double post

This post was edited by HamsterHuey on Wed, Aug 14, 13 at 14:34

Prodiamine (Barricade) is very effective but be careful because it has a long residual - approximately 6 months or so if applied correctly, and can interfere with overseeding plans if applied in spring. Dimension is another good option and lasts approximately 3 months. Halts (Pendimethalin) works reasonably well but is a bit too short lived. It kept the crabgrass at bay in Spring but I've had a major breakout this summer. I'm sure all the rain this summer probably didn't help and might have washed away the barrier.