Can Tenacity kill “good” grass?

Kentucky bluegrass, Fescue, Rye and Bent, etc
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swami7774
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Can Tenacity kill “good” grass?

Post by swami7774 » June 9th, 2020, 11:27 am

SItuation: last week I sprayed Tenacity on a section of newly(last year) planted grass. As the photos show, patches are turning white—including what appears to be non-poa grass. My prior experience with Tenacity is that it killed only poa and some weeds. What does this look like to you? Thanks in advance.
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andy10917
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Re: Can Tenacity kill “good” grass?

Post by andy10917 » June 9th, 2020, 12:57 pm

What rate did you apply it at, and has that grass ever had Tenacity on it before?

swami7774
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Re: Can Tenacity kill “good” grass?

Post by swami7774 » June 9th, 2020, 1:10 pm

andy10917 wrote:
June 9th, 2020, 12:57 pm
What rate did you apply it at, and has that grass ever had Tenacity on it before?
I used the prescribed rate, as best as I could determine from the instructions. And no, that section had never been treated with Tenacity. Other areas have. Recurring poa is an ongoing battle in my yard, and each year I do a “preventive” Tenacity treatment early on.

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andy10917
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Re: Can Tenacity kill “good” grass?

Post by andy10917 » June 9th, 2020, 1:17 pm

There are different rates for different approaches - what is the rate that you applied the Tenacity at - in ounce/per acre numbers of teaspoons/gallon. Your question cannot be answered without that information...

swami7774
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Re: Can Tenacity kill “good” grass?

Post by swami7774 » June 9th, 2020, 1:19 pm

andy10917 wrote:
June 9th, 2020, 1:17 pm
There are different rates for different approaches - what is the rate that you applied the Tenacity at - in ounce/per acre numbers of teaspoons/gallon. Your question cannot be answered without that information...
I tried to edit the above comment to add that info but the site crashed. I mixed a teaspoon into a gallon and used it over a couple of areas totaling about 1k square feet, using a backpack sprayer.


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Re: Can Tenacity kill “good” grass?

Post by northeastlawn » June 9th, 2020, 1:46 pm

The rate at which you applied it matters, I sounds like you doubled the rate. It should be 1tsp per 2 gallons you put down the 8oz rate, a lot of people including my self have done this. Tenacity is an advanced chemical that requires careful measurement and application.

Consider this....

At the typical diagnosis rate of 4oz/AC/1000sf. It will bleach in 10-14 days.

If you did nothing else it will take 10-14 days for grass like PR and FF to recover, KBG typically sees little change.

Thats basically a month of bleaching depending on the wx and growth rate.

So once you put this down, you don't know whats going to happen for about a month anyway. Since you doubled it it will take longer to grow out of, but this comes up a lot and the lawns usually recover.

From me using it; KBG sees little bleaching, PR gets some pronounced bleaching that goes away, and FF really gets hit hard and looks like its going to die. Jury is out whether the FF I sprayed this month will recover or die. I just have to wait and see, you kind of never know when you use it on non KBG.

If things look bad, just call it a day and mark your calendar a month from now and see if the lawn has out grown it. From a lot of posts on here, be sure to water often so the lawn can out grow it.

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andy10917
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Re: Can Tenacity kill “good” grass?

Post by andy10917 » June 9th, 2020, 1:52 pm

That's the 8 oz/acre rate - a pretty heavy hit, but should do no harm. Tenacity seems to have more whitening effect on grass that has never had Tenacity applied to it previously. Most of us apply at the 4 oz/a rate (half a teaspoon per gallon, over 1000 sq ft).

There is a good chance that the whitening is going to go away in 2 weeks.

swami7774
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Re: Can Tenacity kill “good” grass?

Post by swami7774 » June 9th, 2020, 1:56 pm

andy10917 wrote:
June 9th, 2020, 1:52 pm
That's the 8 oz/acre rate - a pretty heavy hit, but should do no harm. Tenacity seems to have more whitening effect on grass that has never had Tenacity applied to it previously. Most of us apply at the 4 oz/a rate (half a teaspoon per gallon, over 1000 sq ft).

There is a good chance that the whitening is going to go away in 2 weeks.
Good point. On the other areas where I’ve used Tenacity before the whitening is noticeably less pronounced.
The power of that stuff is phenomenal. Really have to be careful not to overuse.
Would flushing with water speed the recovery?

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andy10917
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Re: Can Tenacity kill “good” grass?

Post by andy10917 » June 9th, 2020, 2:10 pm

Nope. It's been in the grass plants a long time if it is showing whitening. Since it's stressed a bit, just keep up on regular waterings and give it time to recover.

swami7774
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Re: Can Tenacity kill “good” grass?

Post by swami7774 » June 9th, 2020, 8:29 pm

Thanks!

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Re: Can Tenacity kill “good” grass?

Post by schreibdave » June 10th, 2020, 6:20 am

My kbg is recovering from tenacity spot spray bleaching and I have been watering it more than normal in order to promote more growth and hopefully have it grow out faster.

swami7774
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Re: Can Tenacity kill “good” grass?

Post by swami7774 » June 10th, 2020, 8:31 am

I thought the bleaching was the actual killing of poa and other unwanted stuff.

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andy10917
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Re: Can Tenacity kill “good” grass?

Post by andy10917 » June 10th, 2020, 8:46 am

No, at normal rates all grasses *may* bleach, but most cool-season grasses (with the possible exception of Fine Fescues) will recover, while Poa Annua will continue to progress to death.

swami7774
Posts: 306
Joined: August 13th, 2010, 9:42 pm
Location: Zone 7A(Cape Cod, MA)
Grass Type: Some tall fescues, along with Bedazzled, Bewitched, Blue Velvet.
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Level: Some Experience

Re: Can Tenacity kill “good” grass?

Post by swami7774 » June 10th, 2020, 9:12 am

andy10917 wrote:
June 10th, 2020, 8:46 am
No, at normal rates all grasses *may* bleach, but most cool-season grasses (with the possible exception of Fine Fescues) will recover, while Poa Annua will continue to progress to death.
That’s good to know.

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