Could also be nimblewill as it looks a lot like bentgrass. Pretty sure Tenacity will take care of it either way.

I'll check out nimbleweed and do a little research. Does it grow in cool season lawns? @mishmosh So I was planning on doing a fall pre emergent but if I use the Tenacity, I will have to overseed. So I'm not sure what I will do unless I spray soon and then hope for a long summer. The application of the fall pre emergent would be end of August, beginning of September for annua. Any inputs or strategy that might work I am ears.

what size area needs overseeing? I usually just let my kbg fill in. alternatively you could overseed and just keep using tenacity...either spray or granular in starter.

@mishmosh my front yard is 8500 sq ft. The bent grass is spread through out in patches randomly

Got any pictures? 8500 sq ft is a decent amount but can be easily blanket sprayed with a backpack sprayer. It would be a real chore with a tank sprayer. I like to spray around 1 gal per 1000 sq.ft or slightly less (like 4 gal backpack per 5000 sq.ft.)

The first pics you can see where it's lighter. At first I was convinced it was poa triv based on the look from a far. The color is due to it being matted it down. If I were to straighten those spots out they would be much longer then the rest of the grass. I do believe I have triv also spread in certain spots but I'll wait to tackle that I suppose. The close ups if you take a look at the ligule it is longer more feathery look. The vernation is rolled where as poa is folded and the leaf tip is pointed as well.

Wow. That is some serious contamination. That area near the drain may be hard to control long term if it's wet frequently.

Yeah that area stays moist even during dry spells. I need to start coordinating the tenacity and pre emergent application. For the pre emergent I know it will be around end of August but I’m not sure if that to late in order for me to re seed. Most pre emergents say 4 weeks I believe to reseed but I don’t know if October will be too cold for seed to germinate

not too many grasses do well where it's wet which is why you find creeping bentgrass or POA triv. before you nuke it, first decide if other grasses would do well there. if it's moist most of the time, maybe leave well enough alone. grass is better than no grass

Very good point, thanks mishmosh. There’s a product by scotss called Halt which is a pre emergent. It has the same ingredient as Tenacity. Does a granular pre emergent disrupt the growing pattern of a perennial grass? What in you experience does well in a wet area? I the soil is not constantly drenched. It stay wet because of how it slopes. My whol yard does that. I’m on a corner lot and my house is up high and the most the turf slopes to the road and ditch.

Halts is NOT tenacity. tenacity/mesotrione can be found in Scott's starter fert with crabgrass preventer. Big difference because you can't seed with halts.

Up north, I've only seen creeping bentgrass and poa triv do well in very moist areas... especially with any shade. Kbg can tolerate some spring and fall moist soils. It all depends how bad you think that area is.

I'll probably get some tenacity just to have on hand. I might do sections on the lawn with the Tenacity just so it doesn't get overwhelming when I have to over seeds. Generally how long should I wait to over seed after a pre emergent application? Also can I apply a pre emergent in the spring after I over seed in the fall?

A pre-emergent application is easiest to do with the starter/mesotrione product imho. Otherwise it is too hard to time with rain. If you spray it and it dries before it rains, it's essentially just post-emergent. I doubt a pre-emergent application will kill existing bentgrass...I think you need to spray it for it to die. I think both forms have it's place in seeding even though the starter/mesotrione is rather expensive, about $40 for 5000 sqft application.

They have the scotts halts that just the herbicide and it has Pendimethalin. It says not to use on bentgrass as it might prevent from growing. I'm going to spray half my yard with tenacity so I can over seed it and spread the pre emergent on the other half. The side I over seed with can I use a pre emergent on the following spring?

What about if I just lay sod in the effected parts instead of reseeding? As far as I know pre emergents don't affect sod.

Fall and overwintering is plenty of time for establishment before spring pre-emergent. Pre-emergents can affect sod rooting. Definitely not recommended for newly laid sod as far as I know.