It is poa annua. It is very difficult to get rid of in northern lawns. I'll let the Yankees answer for the details.

Keep that away from me and nuke it from orbit. It's the only way to be sure.

Tenacity will take it out, although it'll also bleach PR/Fescue and may do damage to both as well depending on the cultivar (it is listed for turf type tall fescues and perennial ryegrasses, I've simply noticed it seems to do a little more damage to them than it does to bluegrass, although they certainly do recover from it).

Several applications, several weeks apart, may be necessary to control it, and it's a prolific seeder, so it'll be back.

Use of any good pre-emergent listed for P. annua (I like Prodiamine, but many others work as well...including Tenacity itself, which is a short-term pre-emergent of about 30 days) helps to suppress the seed sprout. P. annua is a fall-sprouting grass, just like any other, and easily survives any northern winter (it's now naturalized itself to friggin' Antarctica as per an arcticle...I mean article I read some years ago).

Use of most pre-emergents will preclude reseeding your lawn since it sprouts at the same time and under the same conditions as your lawn grasses do, but Tenacity application with the lawn seeding will help you out there. It's not perfect, but it helps. The instructions are on the bottle.

Thanks I'll lookup Tenacity. I'm thinking what I'm currently doing and bagging the mowing and disposing of it (including Poa Annua seeds the mower catches) should help matters until I try chemicals. It does chop off many of the seeds. Instead of bagging I think mulching the lawn right now with the mower with Poa Annua seeds on the weed would be a disaster.

If the seeds are mature, yes. Most likely, in May, they most certainly aren't. But not taking chances is also smart, so I certainly don't object in the slightest.

Again, P. annua follows the same life cycle as other grasses. Seed will mature just before the highest summer heat and summer over, sprouting in fall when the rains resume on the high plains. Immature seed, cut off, doesn't tend to survive.

The bad news being that annua is fully capable of seeding laterally as well these days. You never cut off all of it.

The good news is that if you keep a shield of pre-emergent down, the pressure really does drop over the years. These days, I get a patch or three and that's it. A little Tenacity in May and bye-bye until next year.