Most of my lawn was seeded brand new 8 years ago with Pennington Premium which has been GREAT!

The rest was done later with some Scotts seed which has been HORRIBLE! I have more weeds in that section namely foxtail and crabgrass.

So I am considering killing all grass in this area and raking it out then seeding here this month.
Then putting crabgrass halt on it in spring.

Question:
Will this work?
Is there a better way or time?
Will crabgrass halt hurt new grass next spring?
Or what do I do?

How often do you water? or get rain this year?
How high do you mow?
What grasses are in Pennington Premium?

It could be no matter what Scotts Lawn Service did, you set up the lawn for weeds.

You could round up the area and start over. It is getting late in the season, though, so get ready and do it. Now is the time, not next spring if you can help it. If you water and mow properly you should not have much problem next year.

It seems that pre-emergence never works no matter who does it, myself or Scotts lawn service.

Even if the crabgrass dies at end of year, don't the same plants start growing again in spring? By "dies" do you mean lays dormant? Or do brand new ones start and old ones never come back?

Could you pictures of the crabgrass?

If it is foxtail, no wonder the company could not eradicate it for you as there is no selective herbicide for it other than Glyphosate (Round Up) which kills anything and everything.

Problem #2 - How often do you mow. In order for that foxtail to grow that tall and form those seed heads, it must have been a long time between mows. Why? Cultural practices are VERY important to preventing weeds.

Weeds can appear in spots before you know it. If you get a fungus or insect problem, then before you even realize you have a problem the thin spot can happen and the weed seeds germinate.

Annual plants live for one growing season and then die. When they die they never come alive again. These types of plants propagate by dropping seeds. Those seeds germinate and sprout at the next opportunity (which involve temperature, moisture, and hours of direct sunlight).

I would not be certain of why you were getting the summer annuals (crabgrass, foxtails) and perennial weeds in that area without using a soil probe. Any chance the soil is thinner or rockier there? My first and best diagnostic tool has always been a soil probe.

If you have a dense stand of turf and mow at an appropriate height, quite a few summer annuals will be suppressed due to the lack of sunlight reaching the soil where the seeds lay in wait. For this reason, I always recommend mowing at the HIGHEST possible settings in late Spring and throughout Summer. Often, one mowing the wrong time and at too low of a height can invite summer annuals into your lawn. In a wet year (like we had in the Northeast), summer annuals can persist in germinating right through the summer even as your pre-emergent fails. Breakdown is due to sunlight warming exposed soil. This and the heightened soil microbial activity that is brought on by an unduly wet Summer and made worse by close mowing. Rocky soil can also contribute as it heats up easily which stresses the grass, exposes the soil and causes an early breakdown of your pre-emergent If turf density is adequate and your mowing height is (higher)appropriate, I'd expect a much better lawn. If, indeed, the soil is thin and rocky you may be limited by that. You would also normally notice that the turf in those areas shows up as stressed earlier in the season or more easily than the rest of your lawn.

By the way, Halts (Pendimethalin) was great stuff for lawns for years in the 80's. It lasted 6-8 weeks and when applied at the right time was the best thing going for summer annual control. At some point in time it became obsolete (to me at least). I'd not use Halts today if they were giving it away for free. Many products are available with dithiopyr (Dimension) which not only offers POST-emergent control on summer annuals (you can be somewhat late and still get good control -- actually up until the second tiller stage) but it functions for as long as 12 weeks as a pre-emergent. In a wet summer...it will make all the difference in many lawns. And...it's always cheaper where I buy it than it's 'nationally' advertised competition.

As for your lawn, core aerate the ker-app out of it (5-6 passes) and then spread a half-rate of whatever seed you favor. Wait as late as Possible to apply your 2010 application of pre-emergent (see above). I always apply in early May (about 3 weeks after the frantic masses here in central PA have applied their Pendimethalin).

I put some grass seed down in the bare spots and plan to cut grass higher next spring and do multiple halts applications.

Here's another plan I have.
Since the area is a little shallower than the surrounding yard (because it used to be brush before I cut it out and had a bobcat hit it) I was thinking of adding a load of top soil on top of whats there and reseeding next spring.
It would level it and cover everything there and be like starting from scratch.
Will deeper soil discourage those weeds?