Identify This Type Of Grass

[packy51]

The other thing about Tenacity is it has a tendency to temporarily bleach out the area sprayed

 

[kuldeepbaswal]

Based on what you're describing — light green, comes back after Tenacity, grows in patches among fescue — creeping bentgrass is a really solid guess. It spreads by stolons (above-ground runners), has a finer texture than fescue, and tends to form those lighter-colored patches that stand out, especially when mowed at fescue height.
A couple ways to confirm:

• Pull up a section and look for stolons — thin horizontal stems running along the soil surface. Bermuda has these too but also has rhizomes (underground runners). Bentgrass is stolons only.
• Bentgrass loves to lay flat when mowed at normal lawn height — it's designed for putting greens at 1/8" so at 3-4" it just mats down and looks weird compared to your fescue standing upright.
• If Tenacity only suppressed it temporarily, that's consistent with bentgrass. Tenacity will bleach it white but doesn't always kill established bentgrass completely.

To actually get rid of it, you'll likely need to spot-spray with glyphosate (which will kill everything in that area) and then reseed with your fescue blend. Best timing is early fall — kill the patches in late August, wait a week, rough up the bare spots, and overseed.
When you're ready to reseed those spots, make sure you're using a quality fescue blend that'll fill in thick enough to compete. This guide compares some of the better seed options — a good TTTF blend will fill in those bare patches and match the rest of your lawn pretty well.

 

[slomo]

I saw a video on Tenacity last night. It did not do well with a lot of weeds and grasses it should have. Good luck.

Some weeds and grasses build up a tolerance from certain chemicals being sprayed on. Just don't work as they used to. Reason why you should alternate/rotate herbicides and see what is working for you in YOUR yard.

 

[slomo]

So St. Augustine is Fescue from what I am reading online

Don't think so. Lots of St. Aug in Florida.

Fescue is a cool season grass. People up north plant it mostly. You can plant it under trees here in OKC. Shoot now they have drought tolerant frescue hybrids that are a mut mux of different grasses. These tend to be better in hot summers with less water. They are mixed with Kentucky Blue Grass, Rye and so on to get certain properties people want.

 

[slomo]

Getting a good pre-emergent down a couple times a year will help keep weeds and unwanted grasses down. The seeds come in on the wind. That reminds me it is time to do my lawn again before the winter POA starts to take off in a couple weeks.

One season I sprayed pre-emergent every month. Still had weeds. Prodiamine is a huge favorite pre spray in my area. Weeds don't die. They get stunted till next season.

My neighbor had a weed free yard. Company sprayed every three weeks. Due to health reasons they stopped spraying. His yard is a salad bowl again.