My understanding is that a pre-emergent should be applied mid August to prevent poa germination, the later the pre-m the more poa that will get established. You are going to need to choose. Your best route might be to plant this year, use tenacity next year on the poa and apply the pre-m next Fall to eradicate the poa..

Tenacity can be used at seeding as a pre-emergent for poa annua. It should be reapplied four weeks after germination or after the second mowing, whichever is longer. That's the label instructions. Some people do the second application 30 days after seeding as the protection wears off in about 30 days. Dimension can be used later in the fall when the second Tenacity application is wearing off. Tenacity's pre-emergence protection is short-lived but it can protect from poa annua (and other weeds) while your grass is getting established. The time you need to have a pre-emergent down (or already down) is when the soil temperatures start to fall to 70 degrees. When using Tenacity you should read and follow instructions, as it should be mixed and applied precisely to a given area.

Becky. how are you going to get the Tenacity onto the surface of the soil in those thin/brown spots without overdosing so that it can act as a pre-m?

Mahtab3 will be cutting low and bagging as preparation for overseeding and the ground is exposed then. Aim for the ground instead of the grass and irrigate afterwards to wash it into the soil. According to the label a 5-8 oz per acre rate can be used as a pre-emergent. You should practice ahead of time with your sprayer and a tank of water to calibrate your coverage over a given area.

I havent done much research or heard too much about tenacity. What is the difference between tenacity and dimension?

Also, if apply something like tenacity now then would it make sense to overseed in late September?

Dimension prevents seeds from establishing, whether they're "weed seeds" (crab grass, poa annua, chickweed etc.) or turf grass seeds (Fescue, Rye, KBG, etc.). Tenacity is safe for many turf grasses (cool season grasses in particular.) In other words, you can apply Tenacity and it will not impair the establishment of turf grass seed. In fact, it actually has been shown to improve germination. You can sow seed anytime when using Tenacity.

Caveat: Tenacity is more expensive and it does not work as well as Dimension as a pre-emergent.

Tenacity is the only pre-emergent that can be used at seeding that will prevent poa annua germination. Tupersan is the only other pre-emergent that can be used at seeding but it doesn't prevent poa annua germination. The protection is short-lived and you should use Dimension or another normal pre-emergent later when it is safe to use on seedings (read the directions). Don't delay on seeding. You should do it ASAP. Tenacity is $60-70 for a small bottle but you use less than a teaspoon per gallon of water. You will need a sprayer. It needs to be applied precisely. You might get a landscaper to do it for you if you're not sure about what you're doing.

Tenacity, when used as a pre-emergent, is applied at the same time as seeding or a day later. It cannot be applied on young seedlings until they have matured a bit. If you're going to use it, do it at the same time as you seed.

Thank you all for the great advice and knowledge!
I think I will try out Tenacity. Hopefully I can get it from Amazon with a 2 day shipping so I can apply it over the weekend. I will also make sure to put down new grass seeds the same day.
I started doing my own research and Ive read quite a few times that Surfactant should be mixed with Tenacity. What do you think?

The instructions of the bottle read, "Apply Tenacity at 5-8 fl. oz per acre in at least 30 gallons of water per acre". I have a 2000 sq ft yard, any idea how many fl. oz will be needed with how many gallons of water? If I apply too much, will it permanently burn my grass?

Applying too much will bleach the grass, and potentially kill it. I've never seen grass die of the stuff in practice, but I've certainly seen severe bleaching.

As a pre-emergent, application rates are 0.55 to 0.88 teaspoons of Tenacity per 0.7 gallons of water per thousand square feet (you can use more water than this, but don't use less). Really, anything from half a teaspoon to seven eigths of Tenacity is correct.

That amount of product needs to go over 1000 square feet. Mark off 1000 square feet exactly and practice spraying plain water over it. Make adjustments to your sprayer if you can so that one gallon of water will cover 1000 square feet (maybe also adjust your walking speed). Then you can use that amount of product in one gallon and know that it's going over the 1000 square feet.

Cut your grass low before you seed and spray the Tenacity on the ground rather than on the grass. Used as a pre-emergent, it does not need a surfactant. A surfactant would make it stick to the grass and in this case we want it more on the dirt rather than on the grass. You'll be watering and that will help wash it to the ground.

Becky thats a great idea! Ill definitely practice before hand with just water.
I do have one more question before I go if you dont mind answering, what kind of grass seed would you recommend for an area that does not have a lot of shade? My yard is currently a mix between KBG and tall fescue. Should I continue to use the same mix of seeds? or Should I lean towards more of the KBG?

>>My yard is currently a mix between KBG and tall fescue. Should I continue to use the same mix of seeds? or Should I lean towards more of the KBG?

Do you like your mix or wish it were something different? If you'd rather have more KBG, seed it that way.

KBG takes 2-3 weeks or more to germinate, fescue takes 1-2 weeks. Since you're seeding into an existing lawn, I say go for fescue or use your same mix if you have it. KBG will be outcompeted by the existing grass before it can get established. Next year if you want all KBG, plan to kill everything and fallow for a few weeks before planting. Back to Tenacity: if you find yourself running out of water part of the way, you can adjust the dosage per gallon, multiplying the .55 teaspoon by whatever percentage you covered with your practice try. It comes with a syringe to measure. Next year if you have poa annua despite pre-emergents you can use Tenacity at a lower dosage (2 oz per acre) for a few applications. The bottle doesn't say it controls mature poa annua but people have had success with it.

So bleached grass is possible with Tenacity, that would explain a lot for me. Where my yard was sodded with bluegrass i've got rough bluegrass that has gone white after spraying, but where my yard was hydroseeded with a tri mix I have A LOT of grass that has gone yellowish since spraying 12 days ago. I assumed it was all POA T but appears it is also some K31.

Yep, Tenacity works by interfering with the photosynthetic process in some plants that use a certain enzyme. No energy, no sugar, no chlorophyll production (the existing stuff is destroyed by sunlight), turns ghost white, dies.

Partial interference or overuse can result in bleaching even in your bluegrass, fescue, or rye, but in most cases it lightens but has a good chance to recover.

Even normal usage rates visibly lighten bluegrasses, which is why I don't blanket spray Tenacity any longer. That lighter tone appears everywhere and I hate that.

I didn't realize that K31 was susceptible, but let's wait and see if it dies. I have a suspicion that at least most of it will pull through just fine.

I meant by the K31 changing, that it is more likely than not that it is all bleached. I'd love if it killed the K31, but that stuff is a PITA.

Well, at least it points the stuff out for you if you want to remove it with Round Up. Which is about the only thing I found that will kill the stuff, other than digging it out!

I am curious about this, but some post emergent weed kills or weed and feeds burn your grass when applied during the summer at high temperature. Does tenacity have a different effect during different times of the year based on temperature?

As far as I've noted so far--in Pennsylvania summers, which can be steamy and in the nineties--there's no grass burn on Kentucky bluegrass. I have really ridiculously healthy bluegrass, though.

As to effectiveness, it varies by when the weed you're spraying is most active. For crabgrass, it works best warm. For P. annua and P. trivialis, it works best when highs are around 60 (as both hunker down and wait out hot weather). For globe thistle, it doesn't seem to matter and warm or cool, it works in a week.