I'm trying to overseed with fescue in spring and fall to help thinned out summer spots. Fescue like to be planted when soil temperatures are dropping into the 65-60's.

Poa Annua starts it's unforgivable emergence when soil temperatures start dropping past 70 degrees. This overlaps with the prime time to plant fescue in the fall. I also don't fully understand the emergence of Poa Annua in the spring time. I suspect the colder winter temps don't provide an optimal temperature for it, but the spring warmth brings the soil back to 60-70 degrees for the Poa therefore letting it germinate.
In an article I read: http://www.golfdom.com/business/turfgrass-management/spring-and-poa-an nua-is-air , it explains how Poa does NOT need light to germinate and will still grow under the canopy of other grasses. Is that true? I'm growing my TTTF out up to 5 inches to help compete.

My question is, is there a way to keep planting fescue, while using a pre-emergent against Poa Annua? I bet it would be a VERY small window of time. Are there pre-emergents that only prevent Poa from germination and will allow grass seed to go? I would assume the best shot I would have, based on my fescue coming up now, would be as follow-

1. Apply fall Poa Annua pre-emergent control. This would hinder fall Poa germination.
2. Apply early spring Poa Annua pre-emergent control at around 55 degrees in the soil.
3. When soil temps rise past 65, seed fescue.
4. Pray the fescue gets deep enough roots for the Oklahoma heat.

Let me know what you think. Thanks in advance!

Your best bet is to use tenacity in the fall and overseed at the same time. Tenacity will allow the seed to germinate while also acting as a pre and post emergent on the poa

Does Tenacity not effect 90+% TTTF? Most instances I read said that it was used successfully in cool season turfs <20% Tall Fescue. That scares me. Should it not?
Thank you very much for the option!

Absolutely. Want to have some fun? Google "poa annua + antarctic"

You do not state where you live, but here in the Midwest, we can cheat mother nature a little sometimes. Most early to mid Augusts, day time temperature remain warm, but the nights are starting to get cooler. It is this time that here we can cheat and drop seeds.

One needs to baby it very closely, to get germination and growth from the new seedlings with watering, but it can be done.

Then 2 weeks after germination (around Labor Day +/-) drop Dimension, to prevent poa annua from germinating as soil temps drop into poa's preferred range.

*Once again - cheating. Most say wait until 2 mows of the new seedlings before applying preM's, however Zach Reicher of Prudue / now Unv Of Neb studies shows cheating can be done. See link here
http://www.jstor.org/discover/10.2307/3988908?uid=3739656&uid=2129&uid =2&uid=70&uid=4&uid=3739256&sid=55906481363

Tenacity can be used anytime during this period, including seed drop day, and should be applied regularly during the fall for best results.

Then at last cut of the year, apply Dimension again when you winterize with nitrogen - to prevent that "poa annua + antarctic"