I had good luck this year with Acclaim, it's kind of spendy ($90 pint) but it goes a long way. About 1oz per gallon or so and spot treat with a pump sprayer. Works best when weeds are actively growing i.e. don't apply in high temperatures and/or drought. It doesn't play well with 2,4,D so applications have to be staggered.

Not a lot you can do for the crabgrass that has already sprouted if you plan to overseed, except pull them by hand. You can however use Tenacity. Tenacity herbicide may be applied to labeled turfgrasses anytime up to, during and after seeding, but prior to turf emergence. This will help with competition from new weeds. I'll be applying Tenacity as soon as I get the yard prepped for seeding and then overseed around Sept. 15. Tenacity only lasts about a month, so I'll spray again 4 weeks after overseeding, then maybe put down a pre-emergent 4 weeks later as i have a horrible chickweed problem to deal with.

True crabgrass gets going in the spring not at the end of summer. Can you take a picture of the grass you have?

How were you watering over the summer? How often and for how long?

How high/low were you mowing?

Did you fertilize in the past year? If so when and what did you use?

Hi there. We had a colder than normal June & July where I am, it didn't heat up until August. We pulled a ton of crab grass out last year by the roots, so I thought we had nipped it in the bud. Large patches of the crabgrass just exploded on the scene when the weather turned (it is for sure crab grass). The lawn gets watered for an hour three times a week (we have water restrictions), fertilizer and lime on a regular basis and it is being cut at 2 1/2 inches. I could try and kill it with an over the counter product, then power rake and reseed. Or leave it until the frost gets it, power rake in the spring and put a pre emergent down and not worry about overseeding. I just wanted to tap into the vast amount of knowledge people on this site have and see what they would do. I very much appreciate the info coming my way.

If you're going to seed, best to kill it. Quinclorac with Methylated Seed Oil should kill it quick.

You're doomed to get it again if you continue watering like that. Crabgrass seed requires frequent watering - like multiple waterings per week.

Raise your mower to the highest setting to help shade the soil and reduce the chances of germinating new weed seed.

Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the daytime air temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall.

Thanks so much for the watering info; would you try and kill off the crabgrass now then reseed after power raking, or just let the frost take care of it and hopefully reseed in the spring after putting down a pre-emergent? The cold weather grass here is just entering its second growing season and will probably fill in OK if I do it soon. I will have to come across the border to get any kind of crabgrass killer, they don't sell it up here. Thanks again!

or just let the frost take care of it and hopefully reseed in the spring after putting down a pre-emergent?

Definitely don't want to seed after putting down a pre-emergent. Pre-emergent prevents all seed from successfully germinating.

Unless you like crabgrass, it's always best to kill it. It's more important about how you kill it though and that relies on the future plans you have.

I think killing it now with something like weed be gon will allow you to try your hand at an over seeding application right away. Then, in the spring, use tenacity to give another seeding application a shot. Use PreM after that according to the appropriate timing.

if you're happy with coverage come Spring time (KbG will spread) then just lay down a good PreM and follow watering and mowing recommendations.

Have you had a soil test done?

No, I haven't done a soil test. You are right about seeding after a pre-emergent; I was going to wait a couple of months after application to put down seed. I have in ground sprinklers so I can keep the ground moist as it gets hotter. The timing is tight, we have water restrictions that start in June. I like your idea of killing it now, then I will power rake it out once it is dead. The grass around here goes dormant in July/August, which gives the crab grass a good start, especially since I was not watering properly. I cut the lawn much higher than I used too and you can really see the difference in the amount of weeds that have come up, compared to years gone by. I think if I get on it quickly the grass will spread just fine; I will explore looking at the Ortho B, I heard that once crab grass gets to this point nothing short of a nuclear strike will kill it. Thanks again for the advice!

That window where you plan on seeding and watering will be the window for the weeds. The crabgrass seeds that you will be fighting next year are already in the soil, just waiting on the warmer weather and water.

If you don't feel like smuggling chemical across borders, both vinegar & baking soda (NOT together!) will kill Crabgrass. Can you get a preM locally or do you have to smuggle that too?

You can actually bring it across the border, you just aren't allowed to use it. LOL. I do see crab grass stuff in the stores up here in the spring, pretty sure that must be the pre-emergent. I guess it is OK as it only puts a layer on the grass to prevent the seeds from turning into crab grass, but doesn't kill something.