Ignoring them is just fine. If dead, they're not growing, so they're not causing any problems. The dead remains will help hold the seed in place and slow, or stop, it from washing out.

If very long, and in patches large enough to do it, scalping them down with the mower will be more than sufficient.

If you want to expend the extra time (and you have the machine available), you can set the slit/power seeder so that the blades just touch the soil surface and go over the lawn using the machine as a power rake. Then rake up the debris. Do a small area first to see if the result meets your satisfaction.

I suggest you use the Tenacity now in the evening or morning when temperatures are lower (surely it's not 90 overnight!) so you can seed earlier. Maybe consider spot sprays of gylphosate on your weed clumps? That will kill them quicker.

beckyinrichmond, I would love to be able to do that. However, my wife and I work nights. We leave for work around 5 PM and rarely get in the bed before 6:30 AM. Spraying in the evening or staying up to spray in the mornings are pretty much out for us.

What about on your day off? Probably the problem is that it can vaporize and drift if temperatures are high. I recently read over the directions on the bottle (don't have it with me right now) and I don't remember anything about not applying it when temperatures are over such and such, though I do see that in some question/answers on a website (not Syngenta's). Call Syngenta and ask. Good planting, growing days are slipping by, days where your grass could be developing good roots. Spot sprays of gylphosate will kill the weeds quickly. Tenacity is slow to kill and may need reapplication after a couple of weeks to complete the kill. Gylphosate will do it in one shot and you can plant next week.

Day off? What day off? Saturday, the first day off, I still sleep half the day away. I guess I do have that evening though, and I could get up early before church on Sunday and spray some and then again Sunday evening and maybe again Monday morning.

As far as Gylphosate, that doesn't sound like very good advice. Isn't that pretty much RoundUp, which kills EVERYTHING, not just the weeds, and then sterilizes the ground for like 30 to 60 days after where nothing will germinate? If so, how would that help me?

For a late September/early October overseed, which I would consider rather late for southern Indiana, I might go with the spot spraying of Round Up/glyphosate.

The stuff only kills the plants whose greenery it touches (although some minor soil effect has been noted in cases of overapplication followed quickly by extreme rainfall). Upon soil contact, it rapidly binds and deactivates, and then becomes food for bacteria who rather like the stuff and turn it into a small amount of phosphorus for your new lawn.

We don't have a photo, so we don't know how far you've let the weeds run rampant. If it's here and there, spot spraying of glyphosate is fine. If it's everywhere, the Tenacity will be superior as it'll spare the grass if properly used.

I don't remember having seen a temperature limit on the Tenacity, and I've certainly used it myself in higher temperatures. However, as a general rule, I do recommend not applying any herbicide over 85 degrees. For some (not Tenacity), it'll harm the grass. For others, it increases the volatility of the herbicide--not really a pollution problem, it just reduces the effectiveness.

Well, you guys have convinced me. I have some crabgrass that
is hit and miss in small spots around the yard but I also have some pretty good
sized concentrations. Even the smaller spots with just one or two plants, the
plants themselves are mature, large and spread out so that it would be fairly
easy to spray just that plant and not get too much else around it. Also, the
RoundUp I had for another area where I didn't want anything else growing back
for a while was the RoundUp Extended Control. Regular RoundUp says you can
replant after 3 days. So, I think I'm going to try and hit the worst of the
infestation with RoundUp, then I'll go over the whole yard with a light spray
of Tenacity for the Yellow Nutsedge. When the crabgrass starts to knock back
and die off, I'll rent a dethatcher and go over the yard with that, then rent
an aerator, then a power seeder and reseed and fertilize.

Oh, and unless we have an unseasonably cold fall or a really
fast-coming winter, we can stay in at least the mid-40s at night and mid-60s to
mid-70s all the way until Thanksgiving around here. It's really hit or miss
and, my luck, we'll have a really cold fall, but I'm really not too worried
about sowing grass in mid to late September. I've looked at some of the
information from the local county extension agents and they say that as long as
the seed is in the ground by the end of September in our area, the grass should
have time to be well rooted before winter hits. Sometimes it will still be good
when seeding as late as mid-October but, with the way the weather is around
here anything past the end of September and I'd really be pushing my luck.

Soooo, that gives me a month to kill the worst of the
crabgrass, dethatch, aerate, power seed and fertilize. Oh, I need to find the
time to close down and winterize my pool too. It looks like September is going
to be a really busy month! I may have to cancel my vacation days before
Thanksgiving and take a few Fridays off instead to extend a few weekends and get everything in.

Thanks for the advice guys.

- Byron

My daughter back yard is nothing but crabgrass which she has killed. What is best way to remove the dead crabgrass

Again. :-)

It's awfully early for crabgrass. Even so, most now-dead weeds can simply be mowed low to the ground. Hopefully any seed on them is immature or, at worst, also now-dead. If not, you'll likely see it again, and there's also likely an active amount of viable seed on the soil surface.

It's wise to use a weed suppressant that's compatible with grass seed, like Tenacity, when reseeding very weedy soils.