# Poa a and tnex



## g-man (Jun 15, 2017)

As part of a renovation, you get some poa a to break thru. You can also get some in borders or spots in the yard (birds/missed overlaps of prem). Lastly, in well cared and irrigated lawns, poa a can survive the summer.

This spring I had some poa a after my reno. It was mostly along the concrete border and edges. There was one spot in the side yard that was quite large. I did my traditional approach with one 4oz/a rate of tenacity with triclopyr to make the POA a go white. This makes it easier to spot it. I then pull the worst offenders and continue with 2oz/a rate of tenacity as a spot treatment to get it to eventually die.

This year things did not go as plan. The cold/wet spring, too busy with kids/covid I missed the 2oz/a rate applications. I hand pulled from the patch, but it was to large patch. My plan was to mix some glyphosate and just kill the larger section to let the kbg take over.

When I was spraying my first tnex application at 5mL/ksqft/g, I did the normal spray approach. But after spraying the area with the patch, I stopped and dose the patch with the tnex solution. I wanted to experiment and I had nothing to loose, since the plan was glyphosate. I know from multiple reports/studies that poa a, and even kbg, does become phototoxic with high rates of tnex.

A week later this is the results:









I was a bit surprised how well it worked. I cant find more poa a in my yard to test (there is one in the neighbors border that I'm tempted).

Here is how that area looks today.









This is off label, your mileage may vary, do at your own risk, you might kill your lawn or it might not work. Experiment with 5mL into 0.5g and a heavy spot spraying (get it wet). I have very limited data points, so I'm interested to see if someone else gets similar results.


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## g-man (Jun 15, 2017)

@bernstem ^ for your question earlier today.


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## davegravy (Jul 25, 2019)

g-man said:


> When I was spraying my first tnex application at 5mL/ksqft/g, I did the normal spray approach. But after spraying the area with the patch, I stopped and dose the patch with the tnex solution. I wanted to experiment and I had nothing to loose, since the plan was glyphosate. I know from multiple reports/studies that poa a, and even kbg, does become phototoxic with high rates of tnex.


Sorry, you mean you double applied on the patch with the poa?


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## Gilley11 (Nov 3, 2019)

This is really interesting. I've got a neighbor with a beautiful fescue lawn with some bad poa a along one side. He's been asking me to spray it but he was apprehensive about glypho. I'm sure I'll see him tomorrow while I'm helping another neighbor next to him but down a tree and I'll talk to him about it tomorrow.


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## Gilley11 (Nov 3, 2019)

@g-man I'm going to replicate your process to compare the results. 
Was that only with 1 application? If multiple apps how long were they spaced apart? Total time from first app to the last picture?


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## Babameca (Jul 29, 2019)

@g-man That summarizes a few posts around the phenomena. Appreciated. 1 week after app looks very promising. Todays picture (how long since application?) is interesting. I can't say if KBG in the area suffers or it is simply a bit darker as a post effect of the higher rate. Thoughts?


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## bernstem (Jan 16, 2018)

@g-man Thanks!


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## g-man (Jun 15, 2017)

28apr2020 - PGR
02May2020 - first picture
30May2020 - last picture

It is a bit darker, but it did not suffer.


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## davegravy (Jul 25, 2019)

@g-man

Do I have this right - you did a broadcast app of 5mL/ksqft/g and then went over the poa area a second time immediately afterwards so it effectively got a higher rate than the rest of your lawn?

I'd like to try this with aneuw which I understand is the same PGR group as t-nex.


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## g-man (Jun 15, 2017)

Yes on that spot it got an overdose.


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## davegravy (Jul 25, 2019)

g-man said:


> Yes on that spot it got an overdose.


Thanks for clarifying. Was it a controlled overdose or you just went over it a few extra times?


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## g-man (Jun 15, 2017)

@davegravy Uncontrolled, unmeasured, I don't know how much.



> This is off label, your mileage may vary, do at your own risk, you might kill your lawn or it might not work. Experiment with 5mL into 0.5g and a heavy spot spraying (get it wet). I have very limited data points, so I'm interested to see if someone else gets similar results.


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## TheSwede (Jul 10, 2018)

So, I've been struggling with Poa A infestation in my reno this spring (due to the unusually warm and wet winter) and this far north, Poa A has a fair chance to survive the summers so after some research I started with multiple low-rate Tenacity apps to try to supress it as much as possible. @g-man was kind enough to send me a PM of his findings suggesting to try T-NEX as Poa A control. Since I did not want to "steal his thunder" I've kept this for myself until now.

Since this PGR is completely uncharted territory for me and I did not know how my KBG reno would react I did not apply an insane amount of T-NEX but did a ~4ml/1000sqft blanket app. Now, it is hard to say if it was the Tenacity treatment or the T-NEX that did it but I would say that it seems like T-NEX almost acted as a kicker to the Tenacity apps. From beeing yellow but still kind of coping, 90% of the Poa A was all dried up and dead withing a week or two after the T-NEX app.

I have since read up a lot more on PGR in general and T-NEX in particular and it turns out that this far north, the long days and relatively cool climate will shift the target GDD down to shorter application intervals and higher concentrations. I am now following the recommendations from Scandinavian Turfgrass and Environment Research Foundation (http://www.sterf.org/Media/Get/1234/growth-regulation-with-primo-maxx-on-nordic-golf-courses.pdf) and will apply around 11-18 ml/1000sqft every two weeks. Hope that the rate is not a typo in the report!


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## VALawnNoob (Jun 9, 2020)

Hmm is this UNL.edu study saying the opposite?

https://turf.unl.edu/NebGuides/PoaannuaControls2010c.pdf

Trinexapac (Primo or T-NEX) will not help to control annual bluegrass, but will actually improve the health and summer performance of the grass. Research from New York on fairways indicates that any annual bluegrass reduction with preemergence herbicides or Prograss is reversed by using trinexapac (Rossi, 2001) . Trinexapac should not be used in an annual bluegrass control program, but is essential in an annual bluegrass encouragement/management program.


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## SnootchieBootchies (Mar 23, 2021)

Would love to hear any updates on the use of T Nex/Tenacity for the poa control. I did a full Reno on my front yard with KBG last fall (Mazama 50%, Turf Pro Blue 50%). Looked amazing late fall and full of Poa A this spring. I did a tenacity app before the KBG started waking up and have seen some harming effect and was planning on doing more applications once the spring green up is in full swing (it's nearing that point now). Trying to figure best approach to rid myself of the poa, give this KBG a change to spread, and use a fall pre-e to prevent return of poa. I have more T Nex that I'll likely ever need since I've used it for vacations and travel in the past to avoid over growth. I had some minor Poa A issues in the backyard in the past and the pre e and some digging hand digging remedied that, but this is rampant.


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## stevehollx (Apr 8, 2020)

A PGR on Poa A in the spring, even if it doesn't kill the poa, may be enough to prevent it from being able to seed, given that some PGRs also can prevent KBG from seeding? Isn't Poa A close enough to the bluegrass family that it could respond a similar way?


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## TheSwede (Jul 10, 2018)

Well, it is always tricky to give advice since we all have different contidtions to concider. My lawn is located really far north compared to most of you (equal to Juno, Alaska) and is not exposed to the high temperatures most of you guys see in the summer. My situation was that I seeded in August, but temperatures dropped quite fast and then plateaued, so the KBG growth pretty much stopped while Poa A could still germinate. The winter temps was the highest recorded in many, many, many, years with no snow at all so Poa A germinated like never before during the early spring while the KBG was still dormant. Not good at all, for the KBG reno...

With that said, this is how my lawn looked after a couple low rate apps of Tenacity (no T-NEX yet, I believe -to early in the season). You can see how the Poa A is suffering (and the typical patchy growth of newly established KBG lawn):


With that said, doing the T-NEX and Tenacity treatment you need to understand that you are applying Tenacity at a rate that is not recommended and you need to be really observant on what is happening with the good grass so you don't kill it. At one point I decided to stop the treatment because the KBG looked really sick, but after a couple weeks I did a couple more and the end result for me was absolutely fantastic. September, lawn looked like this, with 99% of Poa A gone:


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## SanDiegoLawn (Dec 29, 2020)

Sorry for the dumb question but... I just want to check that by tnex, you mean T-nex plant growth regulator product, correct? Or did you mean a combination solution of tenacity mixed with triclopyr?


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## TheSwede (Jul 10, 2018)

SanDiegoLawn said:


> Sorry for the dumb question but... I just want to check that by tnex, you mean T-nex plant growth regulator product, correct? Or did you mean a combination solution of tenacity mixed with triclopyr?


Tenacity at multiple low rates and T-Nex, the PGR.


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## SnootchieBootchies (Mar 23, 2021)

So mine is probably a few days behind your patchy picture, TheSwede...but equally infested. I'll just stick with spot rate tenacity applications for now and see where that lands me. Perhaps after a few mows I'll try the T Nex. I was looking at Ethofumesate, but the label on Poa Constrictor advises to not use it in spring if not used in the fall. Not sure I can come up with the logic there, but worst case I'll stop watering for a bit in June and let the heat smoke off the poa and use pre-e late August through end of season. Seems this is a common issue with full KBG renovations. Lot of watering presenting ideal conditions for the poa. Thanks for the follow up comments.


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## jvf1095 (Aug 8, 2019)

Interesting way to go. Might think about that next year. For now, already started with tenacity & will go ETHO or prodimine late summer. Not worried about the poa surviving the summer. Have full southern exposure in the back, & with most of the poa cut down to the crown, or nearly so, it should fry.


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