# pre-emergent tenacity and fine fescue



## Belgianbillie (Apr 3, 2018)

So i used a mix of TTTF (4th millenium) and a bunch of fine fescues for dense shade. I was about to put down tenacity today to suppress poa and weeds. I just read that tenacity cant be used when you have fine fescue. What gives! Any other pre-emergents i can put down?


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## CPA Nerd (May 8, 2018)

I believe you should be able to use Tupersan. Jonathan Green makes a crabgrass preventer for new seeding. It's not cheap but I believe it's safe. Double check though. I've never used it myself.


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## Belgianbillie (Apr 3, 2018)

SCotts turf grass starter with weed preventer doesnt have anything on the label but still uses meso the active ingredient of tenacity


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## greengrass (Sep 9, 2018)

Scotts starter fertilizer with weed control has Mesotrione as the weed preventer and label says it can be used with fine fescues. Under where to use https://www.scotts.com/en-us/products/lawn-food/scotts-turf-builder-starter-food-new-grass-plus-weed-preventer


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## Belgianbillie (Apr 3, 2018)

greengrass said:


> Scotts starter fertilizer with weed control has Mesotrione as the weed preventer and label says it can be used with fine fescues. Under where to use https://www.scotts.com/en-us/products/lawn-food/scotts-turf-builder-starter-food-new-grass-plus-weed-preventer


I saw that but i dont know how much sense that makes, its the same active ingredient no?


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## greengrass (Sep 9, 2018)

Belgianbillie said:


> greengrass said:
> 
> 
> > Scotts starter fertilizer with weed control has Mesotrione as the weed preventer and label says it can be used with fine fescues. Under where to use https://www.scotts.com/en-us/products/lawn-food/scotts-turf-builder-starter-food-new-grass-plus-weed-preventer
> ...


Same ingredient. I read the tenacity label and says you can apply to fine fescue, sure you are talking about same product?


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## bgillroy (May 30, 2018)

IIRC, mesotrione's label says using the AI as a prem with newly seeded fine fescue can cause decreased density in the germination.

That's a different application than using the AI as a prem on established fine fescue.


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## ken-n-nancy (Jul 25, 2017)

Belgianbillie said:


> So i used a mix of TTTF (4th millenium) and a bunch of fine fescues for dense shade. I was about to put down tenacity today to suppress poa and weeds. I just read that tenacity can't be used when you have fine fescue. What gives! Any other pre-emergents i can put down?


Yesterday, when I read the above, I knew that within the prior 48 hours, while researching the use of Tenacity on fine fescues for the writeup of my experiment to thin out fine fescue from a northern mix using Tenacity (https://thelawnforum.com/viewtopic.php?f=27&t=5671&start=20#p102353), that somewhere I had read a note from Syngenta that addressed the topic. However, yesterday I couldn't locate the source, and I didn't want to paraphrase, so I didn't reply.

Then, today, in a different thread, another TLF reader (@JDgreen18) posted the quote I remembered, which enabled me to find the original source where I had read it a couple days ago. In any case, here it is:



Syngenta Customer Support said:


> Tenacity doesn't reduce germination of fine fescue seeds but slows establishment of seedlings by 50% to 75% after germination. This renders them very susceptible to heat, drought, disease, and other issues. Any other grasses in the mix will likely take over. In theory this could be counteracted by increasing the % of fine fescue in the mix but then the overall establishment will be very slow. The best strategy is to apply Tenacity as a post-emergence after the fine fescue is established. There are recommendations on the label - 4 weeks after seeding or 2 mowings, whichever is longer.


In any case, I think that's the answer as to what Tenacity (mesotrione) does to fine fescue when applied at time of seeding. Armed with that information, you can decide whether you should use it or not... one could make a case either way, depending upon what you're trying to accomplish and what risks you want to take and which you want to avoid...

I should also note that fine fescue is less tolerant of mesotrione than TTTF (or KBG). Accordingly, you'll need to choose your dosing to not harm the FF, as described on the label.


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## ken-n-nancy (Jul 25, 2017)

After making the above post, I re-read the original question, and it's not entirely clear to me whether the original poster was asking about applying the pre-emergent to a newly-seeded stand of grass or an established lawn.



Belgianbillie said:


> So i used a mix of TTTF (4th millenium) and a bunch of fine fescues for dense shade. I was about to put down tenacity today to suppress poa and weeds. I just read that tenacity cant be used when you have fine fescue. What gives! Any other pre-emergents i can put down?


If the lawn is an established one (i.e. seeded last year or earlier), I'd suggest using prodiamine as the pre-emergent, rather than Tenacity. It will be much more effective, but will mean you can't seed grass for a few months, either.

https://www.domyown.com/prodiamine-65-wdg-generic-barricade-p-2495.html


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## BXMurphy (Aug 5, 2017)

I hate fine fescue. It lays over, looks unkempt, and browns out in summer. I wish Tenacity would kill it.

I have done three apps at the 4 oz./acre rate and it still lives. I have one more app coming up next weekend but I know it just won't die.

Where is my glyphosate?...


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## Alex1389 (May 23, 2018)

BXMurphy said:


> I hate fine fescue. It lays over, looks unkempt, and browns out in summer. I wish Tenacity would kill it.
> 
> I have done three apps at the 4 oz./acre rate and it still lives. I have one more app coming up next weekend but I know it just won't die.
> 
> Where is my glyphosate?...


I believe the Tenacity label states that FF is tolerant of Tenacity up to 5 oz/acre rate per app. Your dosage might have been too low. I know Tenacity killed off some of my FF this year, but I went with a 6 oz/acre rate in my front yard.


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