# Eradicating bentgrass in a PRG/FF blend lawn



## vancwa (Oct 28, 2021)

I'm new to this forum, and have been involved with lawn renovation projects for some time. I live near Portland Oregon in the PNW.

My front yard consists of a PRG/FF blend, and I have various patches of bentgrass that have invaded the lawn. In the past, I have just done a multi-app glyphosate treatment and killed off the bentgrass areas in summer - then reseeded those areas in the fall. That technique works fine, but no matter how well I thought I got rid of it - I'm always left with small patches that return, running through large parts of the lawn. Very frustrating! This is definitely bentgrass, not Poa.

I was hoping to use a selective like Mesotrione, but once read that it may damage or kill my existing desired FF grass. I don't want to do another complete renovation! I could continue to spot treat the bentgrass areas with glyphosate as I have done in the past, but accept that I may never completely eradicate the bentgrass using that technique. I would not do any of this until next year. I'd like to hear from folks who have tried using Tenacity/Mesotrione on a FF lawn - whether your experiences are good or bad.

Any thoughts would be appreciated. Thanks!


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## Green (Dec 24, 2017)

I use Meso on my FF/mix areas once in a while for issues like this. You can use Mesotrione, but don't spray large areas...only where the problem is and a few inches beyond. You'll likely lose or thin out a little of the FF, but you can easily overseed well into Spring, and the PR will develop fast. And then you can overseed better in late Summer if still needed. You'll need 2 apps at the 3-4oz/acre rate (or 2oz/A rate for small spots where you're spraying heavier and need to mix weaker).

In order to intentionally thin out FF, I've used higher rates...5-7 oz/acre, repeated.


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## vancwa (Oct 28, 2021)

Hey Green,

Thanks for the suggestion! I will spot spray bentgrass in spring using a lower app rate.

Vancwa


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## Green (Dec 24, 2017)

vancwa said:


> Hey Green,
> 
> Thanks for the suggestion! I will spot spray bentgrass in spring using a lower app rate.
> 
> Vancwa


Yeah. Just make sure to do at least 2 apps. And use the nonionic surfactant. Once it whitens, spray the second app.


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## vancwa (Oct 28, 2021)

Will do. I have that surfactant already and would use it during the app. Thanks again.


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## Green (Dec 24, 2017)

vancwa said:


> Will do. I have that surfactant already and would use it during the app. Thanks again.


One final trick: mix weaker than desired (1.5-2 oz per acre or half desired rate). And then spray over the area lightly, twice as many times as normal. Gives more control over rate and reduces chances of over applying when spot spraying.


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## frostyshake (Jan 3, 2021)

I'm also in western Oregon and have applied tenacity the last two seasons to control bentgrass. I used the rate on the label for bentgrass and applied the three apps two weeks apart. The tenacity knocked bentgrass back, but didn't completely kill it. You are probably looking at applying every year if you really want to minimize the bentgrass. It just grows too well in our climate and is too widespread to eliminate it once and have it stay out.


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## vancwa (Oct 28, 2021)

frostyshake said:


> You are probably looking at applying every year if you really want to minimize the bentgrass. It just grows too well in our climate and is too widespread to eliminate it once and have it stay out.


Thanks for responding. Wow that's disappointing! I may just go back to using Roundup on those sections, then re-seed in the fall. I imagine part of my problem is that I don't kill beyond the bentgrass patch, and invariably miss some hidden stolons are still there that continue to propagate. I would be smarter to just extend the size of the Roundup patch while I'm in nuke-mode.


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## cleohioturf (Jul 20, 2020)

bent grass at higher than green or fairway height needs multiple rounds of meso.

I really dont find meso being a great product for post emergence, its good for a short lived pre emergent while safe for seeding, thats the sweet spot.


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## Green (Dec 24, 2017)

cleohioturf said:


> bent grass at higher than green or fairway height needs multiple rounds of meso.
> 
> I really dont find meso being a great product for post emergence, its good for a short lived pre emergent while safe for seeding, thats the sweet spot.


Like you said, it needs 2-3 apps (of least 3oz per acre rate) for Bentgrass control. And a nonionic surfactant. Plus diligence and keeping an eye out for any that might pop up again over the following year or so.


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## SteelCutLawn (Jul 12, 2021)

I just went through a similar battle using mesotrione for zoysia in cool season lawn. Multiple blanket applications seems to have eradicated zoysia (planning on an app or two next late spring) but FF was smoked!


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## LawnDetail (Apr 15, 2020)

lawnferry6558 said:


> I just went through a similar battle using mesotrione for zoysia in cool season lawn. Multiple blanket applications seems to have eradicated zoysia (planning on an app or two next late spring) but FF was smoked!


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