Is this the correct plan for killing bentgrass with tenacity?

Kentucky bluegrass, Fescue, Rye and Bent, etc
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southern-ct-4
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Is this the correct plan for killing bentgrass with tenacity?

Post by southern-ct-4 » September 9th, 2020, 3:57 pm

3 applications, 14 days apart, starting late August/early September, at a rate of 4oz/acre?

And when is the latest that it's ok/effective to spray?

Finally, to confirm, for 4 oz/acre it's .5 tsp in a 1 gallon (or 1 tsp in a 2 gallon) pump sprayer, and that can be used to spot spray 1k sq ft?

Thank you!

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ken-n-nancy
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Re: Is this the correct plan for killing bentgrass with tenacity?

Post by ken-n-nancy » September 9th, 2020, 5:34 pm

Yes, I think all of what you have written above is good.

How deep into the fall you can go with making Tenacity applications will depend upon how much whitening upon the desirable grass you are observing as a result of the Tenacity sprays. If you are seeing no effect upon the desirable grass (the good grass is staying green instead of getting whitened), then I don't see why you couldn't continue the Tenacity applications until the bentgrass is gone or the ground is frozen, whichever comes first.

If, however, you are seeing whitening of your desirable grasses, I'd suggest making the last spray of Tenacity 4 weeks before you typically have cessation of top growth in your lawn, to give any desirable grass time to recover from the Tenacity before winter.

If you don't know when "cessation of top growth" typically happens for your lawn, you can use "Average First Frost" (see the web page for Dave's Garden Freeze / Frost Dates by Zip Code as a proxy for the day of "4 weeks before cessation of top growth." Personally, I've found my cessation of top growth to be about 7-8 weeks after the nearest "average first frost" for my area.

I should also note, since I mentioned "average first frost" in this conversation, that I have found the time of "cessation of top growth" to be very predictable in my lawn -- it seems to be well-correlated with the calendar, and poorly coordinated with the "actual first frost." In other words, "cessation of top growth" is best predicted by the calendar (where the sun is in the sky and the length of the days) rather than the actual weather. When I was first getting into this lawn care hobby, I would have found that to be surprising. However, now that I've been doing this for more than a few years, it doesn't surprise me at all and makes a lot of sense.

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Re: Is this the correct plan for killing bentgrass with tenacity?

Post by Pway » September 9th, 2020, 5:42 pm

I recently completed three applications at the 4 oz rate about a week apart. Plenty of whitening of the bent for sure. I raked the areas, seeded, and top dressed with peat moss. I’m pretty sure I didn’t kill it all, unfortunately. As I’ve been watering some of it seems to be coming back. In retrospect, I wish I did a fourth application or just nuked the entire front lawn. This bent grass came from deer or bird droppings, I’m 99% sure (haven’t used any seed but gold tag for at least 7 or 8 years.

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Re: Is this the correct plan for killing bentgrass with tenacity?

Post by southern-ct-4 » September 10th, 2020, 9:18 am

Great, thank you very much.

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Re: Is this the correct plan for killing bentgrass with tenacity?

Post by Green » September 10th, 2020, 10:32 pm

Are you sure it's not Nimblewill, or that some could be? If so, you really need to be on it ASAP, before it goes dormant. I'm in the middle of that right now. Otherwise, the only thing I'll add is spray subsequent apps when it goes very white from the previous app, making sure to use your NIS.


southern-ct-4
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Re: Is this the correct plan for killing bentgrass with tenacity?

Post by southern-ct-4 » September 11th, 2020, 8:42 am

I don't think it's nimblewill but i'll try to look closer. Also, even before I asked my question I had sprayed tenacity on 9/5 (a little heavy perhaps) and wow is my lawn lit up... I'll post a picture later (right now the sun is too glary).

At this point I'll just keep hitting it every couple of weeks with the 4 oz rate and see what happens.

Not sure how long I can keep doing this every year several times a year in different spots. Each time I think I have an area under control, it (whatever it may be) pops up in another area (and/or the same area...).

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Re: Is this the correct plan for killing bentgrass with tenacity?

Post by southern-ct-4 » September 11th, 2020, 3:59 pm

The part at the top middle of the pic (near the shrubs by the end of the driveway) is stark white (as are some smaller areas to the right along the driveway). The rest is more yellow/white (though may just need more time to turn white, or perhaps was white and is now dying).

Image

Image

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ken-n-nancy
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Re: Is this the correct plan for killing bentgrass with tenacity?

Post by ken-n-nancy » September 11th, 2020, 4:26 pm

southern-ct-4 wrote:
September 11th, 2020, 3:59 pm
The part at the top middle of the pic (near the shrubs by the end of the driveway) is stark white (as are some smaller areas to the right along the driveway). The rest is more yellow/white (though may just need more time to turn white, or perhaps was white and is now dying).

Image
Looking good. Keep hitting those spots every 10-14 days with another round of Tenacity. The whitening effect usually peaks around 10-14 days, and you want to hit it again just before it starts recovering at all.

Is it just the bentgrass that is having the significant color change? The desirable grass doesn't show significant visible effects?

southern-ct-4
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Re: Is this the correct plan for killing bentgrass with tenacity?

Post by southern-ct-4 » September 11th, 2020, 4:35 pm

ken-n-nancy wrote:
September 11th, 2020, 4:26 pm
southern-ct-4 wrote:
September 11th, 2020, 3:59 pm
The part at the top middle of the pic (near the shrubs by the end of the driveway) is stark white (as are some smaller areas to the right along the driveway). The rest is more yellow/white (though may just need more time to turn white, or perhaps was white and is now dying).

Image
Looking good. Keep hitting those spots every 10-14 days with another round of Tenacity. The whitening effect usually peaks around 10-14 days, and you want to hit it again just before it starts recovering at all.

Is it just the bentgrass that is having the significant color change? The desirable grass doesn't show significant visible effects?
Thanks. I think it's mainly just bent and/or triv, but perhaps some good grass as well (but not a lot I don't think). i'll try to go a little light on what i think is good grass. then again, at this point i don't really care if it damages a bit more than i want it to. I'd rather just be sure to kill of the bad stuff.

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ken-n-nancy
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Re: Is this the correct plan for killing bentgrass with tenacity?

Post by ken-n-nancy » September 11th, 2020, 4:40 pm

southern-ct-4 wrote:
September 11th, 2020, 4:35 pm
... at this point i don't really care if it damages a bit more than i want it to. I'd rather just be sure to kill of the bad stuff.
Good plan. Making sure to get all of the "bad grass" with a little collateral damage to the "good grass" is a far better situation than having no damage to the good grass, but not actually getting all of the "bad grass."

southern-ct-4
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Re: Is this the correct plan for killing bentgrass with tenacity?

Post by southern-ct-4 » September 11th, 2020, 4:44 pm

Agreed! Unfortunately, past few years I seem to kill both good grass and bad grass, and the bad stuff still comes back! :(

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Re: Is this the correct plan for killing bentgrass with tenacity?

Post by Tanksfurnutin » September 18th, 2020, 4:57 pm

I'm in the middle of doing the same and my lawn looks very similar to yours. I was wondering if you guys would continue fertilizing while doing the Tenacity applications. I already put down Milorganite about a month ago and was going to put down some urea this weekend along with the second Tenacity application.

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