# Accidental K31 overseed in KBG/TTTF lawn



## GuitsBoy (4 mo ago)

I'm hoping you guys might be willing to sanity check my salvage attempt.

I know I'm not the first, but I may be the most recent to pull this bonehead move. I have a mixed KBG/TTTF 4k sq ft lawn right now, primarily KBG, maybe 80%/20%. Last year I overseeded KBG only, so this year I wanted to overseed a mixed seed again to introduce a bit more TTTF back into the lawn. In an effort to avoid the scotts/pennington coating tax, I searched for "kentucky bluegrass tall fescue seed" in amazon and was greeted by a number of choices. I picked a highly rated one, and read a few of the best and worst reviews, and pulled the trigger. It arrived while I was home alone with my 3 year old daughter, mid tantrum. I figured having her help me overseed the yard would be a nice way to occupy her for a bit. It wasn't until I was putting remaining 1/3 bag back into the garage that I noticed it made no mention of "bluegrass" only the words "kentucky 31 tall fescue". Here in suburban Long Island NY, K31 is a completely foreign animal, so like most people in the area, I'd never heard of it before. A quick google search later, I was violently nauseous, losing sleep for the next two nights worrying about how to address it.

My first inclination was apply a pre-emergent as quickly as possible, both right now, and again in the spring. This may have helped, but probably wouldn't completely keep the k31 from coming up in ugly clumps in the spring or next fall. And should the preM fail, the only recourse would be to hit the whole lawn with glyphosate multiple times and starting a very lengthy reno, with a lot of time spent with a dead lawn. This would be an incredibly hard sell to the wife and family. After doing quite a bit of reading, I see a few others have run into similar issues, and some have had success using Certainty to selectively kill both the K31 and TTTF. That seems like a compromise I'm willing to take.

I'm currently 6 days after overseeding with K31, and have already ordered the certainty which should arrive later this week. I did not put down a preM because I believe I actually WANT the K31 to germinate, then to kill it while young and weak. I'd also like to re-overseed with KBG after the certainty. I have also just put down a nitrogen heavy feeding, my reasoning that it will further weaken the young seedlings, while strengthening the mature KBG before it gets hit with the certainty. Hopefully that doesn't bite me in the butt.

Here is my current plan: 
I'd like to hit the whole lawn with a single .37 oz/acre dose of Certainty this year. I dont plan to use blue indicator/dye, I'll simply load up the 2 gal sprayer blanket the full lawn three times. I'm pretty used to the spray pressure and pattern to budget a 2 gal sprayer across my full lawn. Doing it in three passes allows me to approach from different angles, which I believe will help minimize overlap and lead to a more even application. I'm planning to use a slightly lower dosage than the typical .5 or even .75 doses, since I mainly want to kill off the young K31. If it does take out the TTTF mix, I'm fine with that, and will concentrate on a KBG only lawn for the next year, before deciding if I eventually want to mix TTTF back in or not. Two to three weeks after spraying the certainty, I'd like to overseed with KBG only. A little late in the game for KBG seed, but again, anything I can do to strengthen and fill out the KBG this fall, the better. After the spring green up I'll use a preM as usual. And once the lawn is in full growth mode, I'll hit the lawn with two more applications of certainty with the usual 28 day spacing, killing off any straggling K31 that survives, or manages to germinate next spring. If I do decide to eliminate all TTTF, I'll continue to spot treat as needed.

Does this sound like a reasonable plan to try to salvage the lawn without a complete reno?

Last couple questions; How should I address treating the sedge I have in a few areas? Its been over 4 weeks since I last hit it with the sedgehammer, since I didnt want it to interfere with overseeding. Should I hit it with the hammer again, since Ill be waiting 3 weeks after the Certainty to overseed anyway? Might as well, right? Also, how should I feed the lawn? Ive seen mention of spoon feeding the KBG lawn with .25 lb / M nitrogen to aid in recovery? Not sure this is advisable to do if I plan to overseed a week later. Should I use a new grass food instead? And lastly, should I dethatch the lawn this fall in an effort to mechanically disturb any young seedlings? Or is that simply a waste of time?

Thanks much for any suggestions, words of wisdom, tales of caution, or outright laughter at my expense. Cheers!


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## Tungsten (6 mo ago)

I don't have a perfect answer. But if this happened to me, I would first try to vacuum as much of the seed as possible with a shop vac. Then put down a pre-emergent. Then pray that not too much comes up.

Pre-emergent does not prevent seeds from starting to germinate. When the seed starts to germinate, the pre-emergent prevents root development, killing the plant.


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## GuitsBoy (4 mo ago)

Thanks Tungsten. The stop vac was a non-starter. I tried it, but it was a bit like trying to un-butter an english muffin. Too many nooks and crannies.

The downside of a pre-emergent is that it would prevent me from putting down any seed at all this year. I do have some thin spots. Is there any specific advantage to using a preM over using certainty?


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## Tungsten (6 mo ago)

PreEm is easier and cheaper and won't kill your good grass. Fall nitrogen blitz can get your existing lawn to fill in thin spots without over seeding.

Did the KY31 start sprouting yet? Maybe someone else can give their input.


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## GuitsBoy (4 mo ago)

Yes, the KY31 has started sprouting, not a ton, but I've got some small sprouts. The certainty should be here in another day or two. Its not cheap, but its less costly than a full reno, at least in terms of work.

There are a few areas Ive been battling sedge that are quite bare, which is why I really want to try to seed this year.

But yes, I do understand that theres a lot more room for error with a preM.


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## Green (Dec 24, 2017)

This is experimental, but I would consider spraying a broadleaf herbicide tank mix like 2,4-D plus Triclopyr if you have weeds anyway. That should take out what is germinating plus your broadleaf weeds. Then in two or three weeks, you can overseed. (Though that might be a bit late.)

If you're not set on overseeding, I'd spray a pre-M as well, and keep the barrier up through the Spring. Dimension sprayed would likely be the best option in this case, as it takes out stuff that is germinating if used at a high enough rate.

Edit: I noticed you're planning to use Certainty. Note you can only use a single app at 0.25 (or maybe up to 0.37) oz per acre on your established Tall Fescue without killing it outright. 0.50 oz per acre would be pushing it; no guarantees. You also cannot overseed after it, just as with the broadleaf herbicides. There is a wait of several weeks. You need to use a non-ionic surfactant. If you have any Poa Triv, it will put a major hurting on it as well, which is good. You should Nitrogen blitz your lawn starting about two weeks after the Certainty application to help it recover. It may not fully recover in time for Winter, and may become more prone to rust fungus this Fall as a result, as well, so you may need to deal with that.


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## GuitsBoy (4 mo ago)

Thanks Green. I dont mind getting rid of the established tall fescue, its a bit patchy anyway. It blends, but its definitely not homogenous. The few cold season certainty threads show a lot of people applying in the .5 to .75 range which definitely hurts the KBG, which is why I wanted to dial it back slightly to the .37 range. Ive read that you can seed after 2 weeks, especially if KBG wont germinate for a while anyway. And yes, I have and plan to use the NIS. Luckily I am not prone to Poa or rust that I know of, but who knows what the future will bring.

The 2,4-D and preM is a good suggestion, but once again, it prohibits me from seeding this year. The certainty seems to be the only chance I have at throwing seed down any time soon. And it seems to be either a once in a million success, or setting myself up for total devastation.

Thanks for adding to the advice.


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## Fraust (Apr 4, 2021)

If your plan is to wait a bit and let as much of the k31 germinate and start growing as you can, then try and kill it, and then still reseed this year, I don't see any way you're going to be able to seed with KBG. You'll be too late in the season for such a slow starting grass. You may not even have enough time for TTTF. I'm not familiar with Certainty specifically, but many herbicides have wait periods after application before seeding. So, you're looking at another week or two to hopefully let it all germinate, possibly several Certainty applications over a week or two, and then another couple week wait to reseed?

I know it's too late now, but I think your best course of action would have been going with a pre-em as soon as you realized and not worrying about any seeding this year, and just really feeding the grass you have. At this point, I don't have a lot of good suggestions unfortunately though. Good luck


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## Green (Dec 24, 2017)

GuitsBoy said:


> Thanks Green. I dont mind getting rid of the established tall fescue, its a bit patchy anyway. It blends, but its definitely not homogenous. The few cold season certainty threads show a lot of people applying in the .5 to .75 range which definitely hurts the KBG, which is why I wanted to dial it back slightly to the .37 range. Ive read that you can seed after 2 weeks, especially if KBG wont germinate for a while anyway. And yes, I have and plan to use the NIS. Luckily I am not prone to Poa or rust that I know of, but who knows what the future will bring.
> 
> The 2,4-D and preM is a good suggestion, but once again, it prohibits me from seeding this year. The certainty seems to be the only chance I have at throwing seed down any time soon. And it seems to be either a once in a million success, or setting myself up for total devastation.
> 
> Thanks for adding to the advice.


FYI, I can just barely most times get away with a single Certainty application at 0.50 oz per acre and not kill my TTTF. I think spraying it as soon as the KY-31 has mostly all germinated is the best bet. KY-31 is pretty fast, almost like Perennial Ryegrass, so it should only take about 10 days for it all to pretty much come up.

Certainty requires 2 gallons of water per thousand square feet, so here is what I would do:
-Spray one set of passes (half the mix in one gallon)
-Let dry
-Spray the second set of passes in the perpendicular direction

This will get the best coverage. Letting it dry between the two sets of passes allows for some of the herbicide to start absorbing, and not wash off the plants.

If your new KY-31 does not totally die from it for some reason, you could try to hit the whole lawn with the 5-6 oz per acre rate of Tenacity two weeks later at overseed time. Thankfully, on LI, you have a long seeding window in the Fall, almost as wide as states significantly further South. Significantly wider than the window on the CT or NY mainland just miles away. That said, there is not a ton more time for KBG seed this year; maybe 3 weeks for you...? I daresay you will have no Poa annua after doing this double treatment (if you have any).


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## GuitsBoy (4 mo ago)

Green, I really like the idea of tenacity at seed down. I hadn't considered that.

So here's my thinking. The KY31 has been down 7 days today. Temps and conditions have been favorable, and I have been irrigating lightly twice a day. The certainty should arrive tomorrow. This sunday, I'll hit the lawn with a .37/A dose certainty, from three different directions (three passes of 2 gal each mixed at .5oz/acre rate, sprayed over the whole 4k sq ft, works out to be .37 oz/acre dose). Two weeks later I'll overseed with KBG, and as suggested, spray with 5oz/acre tenacity at seed down.

In the spring, I'll use a preM and potentially blanket the yard again with certainty to remove any straggling KY31, or possibly any established TTTF I may wish to remove.

Assuming the above looks like a plan, what should I do about my sedge now? Do I hit it with the sedgehammer and hope I can still seed in two weeks? Neither certainty nor tenaicty seems particularly great at removing sedge. In some very thin spots, I could potentially glphosate the patch and just reseed from scratch, but I really hate the idea of doing that. Maybe I just address the sedge better next year, since the cold will kill it off soon anyway?

Thanks again for the suggestion.


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## Green (Dec 24, 2017)

@GuitsBoy

No problem. But you really don't need all that water. Just use the minimum possible according to the Certainty label. 2 gallons total per thousand is enough. You don't need 6 gallons or whatever unless you need that much in order to spray with your specific sprayer (2 per split app). That extra water will just wash the herbicide away.

Also, as it works both foliar and root: Make any irrigation sessions short in the following weeks. You only want the Certainty to enter the roots of the new grass once it gets to the soil (and some will) but not the older grass. It's easy to push it below that level with too much watering.

https://www.solutionsstores.com/sulfosulfuron

If you had an extra week, I would split the apps up even further with more time between them (2 days, a week, etc.). But you don't have time on your side and have to do a condensed version and hope for the best.

And you can always pre germinate seed, I suppose.

Certainty plus Tenacity will likely kill your sedges better than Sedge hammer would have. Warm season people use Certainty for this use. If just one patch, go slightly heavier on the Certainty there, too. I never had sedges where I used Certainty...it kept it in check.

Finally: Certainty will kill some KBG cultivars. Those related to Northstar are among the ones damaged/killed. Hopefully not yours.


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## GuitsBoy (4 mo ago)

I as going to do it a bit short on water at 6 gal split over the 4K sq ft. So thats only 1.3 gal per 1k. Simply because I'm most comfortable budgeting out a full 2gal sprayer over the full yard. But if it will make a considerable difference, Ill simply mix it down further, and go over in four passes, or learn to spray a heavier coating to get the 2gal per 1k sq ft.

Good to know about the sedge, though it is late in the season anyway. Ill have to do a better job of preventing it in the spring and summer next year.

My concern over pre-germinating the seed is that it gives less time for the certainty to fade, and it also makes the seedlings more susceptible to the tenacity. If I'm understanding correctly tenacity is OK at seed down since the seed contains everything the grassling needs early in life, however once it starts relying on photosynthesis, the tenacity would affect it. Pregerminating the seed brings it a week or so closer to this point, no?

So I guess the balancing act becomes, hit it with a two smaller doses of certainty this season, but prolong seeding by a week. Or hit it with a second and/or third dose next spring? Which is the better path?

I have no way to tell what the lawn was originally seeded with, but looking through my past and present labels, I don't see Northstar listed, though one big box mix does have "Starr"

Thanks again for your thoughts and suggestions here.


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## Cdub5_ (Jun 12, 2019)

I say apply pre emergent immediately. Chalk this season up as a loss and pick up possibly next spring.
I'd rather protect my lawn from K31 then have it grow in and end up needing a complete renovation to kill it off next year.

You can still do a fall nitrogen blitz. Who knows, you may like the results you get when you feed your lawn so much nitrogen :mrgreen:


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## Green (Dec 24, 2017)

GuitsBoy said:


> I as going to do it a bit short on water at 6 gal split over the 4K sq ft. So thats only 1.3 gal per 1k. Simply because I'm most comfortable budgeting out a full 2gal sprayer over the full yard. But if it will make a considerable difference, Ill simply mix it down further, and go over in four passes, or learn to spray a heavier coating to get the 2gal per 1k sq ft.
> 
> Good to know about the sedge, though it is late in the season anyway. Ill have to do a better job of preventing it in the spring and summer next year.
> 
> ...


Yeah, everything is going to be a balancing act. Here, not all that far away technically, it's way too late to do much of anything with KBG seed. Hopefully you figure out the right balance. It sounds about right above. The Tenacity shouldn't bother the seed, even at up to 6oz per acre, if applied before or at seeding. One tip: use a little NIS with it and apply in plenty of water in the afternoon or evening. Let it sit overnight. Then water in lightly with just 0.1 to 0.2 inch of water the next day, ideally before the lawn dries, to get every bit of the soil applied pre-M effect (as well as the full post-M effect to damage the seedlings more).


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## GuitsBoy (4 mo ago)

Cdub5_ said:


> I say apply pre emergent immediately. Chalk this season up as a loss and pick up possibly next spring.
> I'd rather protect my lawn from K31 then have it grow in and end up needing a complete renovation to kill it off next year.
> 
> You can still do a fall nitrogen blitz. Who knows, you may like the results you get when you feed your lawn so much nitrogen :mrgreen:


Thanks for chiming in, Cdub5. I still think I'm going to go with the certainty and try to convert to 100% KBG this coming year, then decide if I want to re-mix TTTF back in. If it wasnt for the very thing spots where I did some irrigation work, and where Ive been battling the sedge, then I might have relied on the blitz to get the KBG to fill back in, but I think the areas are a bit too wide, and really need seed. This was enough to tip my hand. And at this point, some of the seed has already germinated by over a week. The PreM might still work, but I think the certainty is going to hit it much harder, even at a lower dose. Still, thank you for your thoughts, the preM is a solid option, even if its not the direction wind up going.


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## GuitsBoy (4 mo ago)

Green said:


> Yeah, everything is going to be a balancing act. Here, not all that far away technically, it's way too late to do much of anything with KBG seed. Hopefully you figure out the right balance. It sounds about right above. The Tenacity shouldn't bother the seed, even at up to 6oz per acre, if applied before or at seeding. One tip: use a little NIS with it and apply in plenty of water in the afternoon or evening. Let it sit overnight. Then water in lightly with just 0.1 to 0.2 inch of water the next day, ideally before the lawn dries, to get every bit of the soil applied pre-M effect (as well as the full post-M effect to damage the seedlings more).


Thanks again for your advice here. Ill give it a go this coming sunday, and hope for the best. Its cold and windy today, but we've had some warm octobers and novembers in recent years. Hopefully its enough to get the KBG seed to dig in. Ill update on how things go.


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## g-man (Jun 15, 2017)

Many have killed their lawns using certainty. Be careful with overlaps and carrier rates.


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## GuitsBoy (4 mo ago)

g-man said:


> Many have killed their lawns using certainty. Be careful with overlaps and carrier rates.


Understood, thank you. I'm hoping to err on the conservative side. Id rather have to touch it up next year, rather than nuke spots this year.


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## Green (Dec 24, 2017)

GuitsBoy said:


> g-man said:
> 
> 
> > Many have killed their lawns using certainty. Be careful with overlaps and carrier rates.
> ...


Very true. Funny old story: The person I bought my bottle from accidentally nuked his lawn with it before selling it to me! I've yet to nuke more than small spots with it, and I've blanket sprayed many times. Most of those nuked spots were spot sprays from last Fall with repeated apps. But I will say the damage potential goes higher starting this time of year in my experience. I would not go above that single 0.375 oz per acre app right now. Following with Tenacity at the two week mark is still risky, but is much, much safer than a second app of Certainty. Plus you have two modes of action. Fescue seedlings hate Sulfosulfuron, and hate Mesotrione.

Regardless, any lingering damage from the one medium rate app shouldn't be anything you can't fix fully next Spring. I think your KBG seeding is more likely to be the issue given the season. But if you have full sun and a warm October, it may do ok, as you alluded to,

Finally, don't be alarmed when you don't see anything happening a week later. It takes a week and a half or so.


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## GuitsBoy (4 mo ago)

Well, its a done deal now. Spent between two and three hours spraying this morning, just before the wind really picked up. I sprayed a total of 6 small scoops of Certainty, mixed between 8 gallons of water, and sprayed over 4,000 sq ft. I wound up doing four passes in total. Straight on, perpendicular, 45º in one direction, and 45º in the other. I aimed for a 50% overlap. The coats were fairly light, but built up in aggregate. Doing it in so many passes allowed me to feel pretty comfortable the end result was a fairly even application. I could adjust my walking speed on the final pass to make sure I didnt run out of product in the middle of a section. The weather is cool and overcast today, with 1/8 inch of rain likely overnight, well after the certainty should be rainfast.

I guess there's not much to do but sit back the next two weeks, and wait till I can apply tenacity and seed. I'll expect the lawn to look pretty crummy around this time, but will hopefully start to bounce back after 3-4 weeks. Maybe I wont go too short on the cut before overseeding since the established KBG will already be weakened by the certainty. I might put down a starter fertilizer just to give the KBG something to help rejuvenate it. I guess we'll see what it looks like in a few weeks.

Thanks again, all.


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## Green (Dec 24, 2017)

GuitsBoy said:


> Well, its a done deal now. Spent between two and three hours spraying this morning, just before the wind really picked up. I sprayed a total of 6 small scoops of Certainty, mixed between 8 gallons of water, and sprayed over 4,000 sq ft. I wound up doing four passes in total. Straight on, perpendicular, 45º in one direction, and 45º in the other. I aimed for a 50% overlap. The coats were fairly light, but built up in aggregate. Doing it in so many passes allowed me to feel pretty comfortable the end result was a fairly even application. I could adjust my walking speed on the final pass to make sure I didnt run out of product in the middle of a section. The weather is cool and overcast today, with 1/8 inch of rain likely overnight, well after the certainty should be rainfast.
> 
> I guess there's not much to do but sit back the next two weeks, and wait till I can apply tenacity and seed. I'll expect the lawn to look pretty crummy around this time, but will hopefully start to bounce back after 3-4 weeks. Maybe I wont go too short on the cut before overseeding since the established KBG will already be weakened by the certainty. I might put down a starter fertilizer just to give the KBG something to help rejuvenate it. I guess we'll see what it looks like in a few weeks.
> 
> Thanks again, all.


Sounds like you did everything right and have a good attitude and the right expectations. Keep us updated how this goes.

I would never have suggested this method to anyone (actually it didn't even cross my mind originally to use Certainty for this issue) but since you were set on it, I wanted to share my experiences using it so you'd have the best chance. It will be interesting to see what happens. Hopefully the seedlings get zapped.

Biggest thing is going to be potential disease pressure now, I think. The grass won't have the normal resources to fight it. Be prepared in case you need to ID lesions, and treat with an appropriate fungicide.

Also, when you do seed, you will probably want to do something to get good seed to soil contact, whether that's dethatching, raking aerating, peat moss, or whatever. Also, pre-germination seed priming is possible for 2 days or so. Advice I got was to put the seed in a paint strainer bag, soak it for a few hours, then remove the bag and let the excess water stay, resubmerging whenever it starts getting dry (but not leaving it submerged all the time). I'm not sure how you'd dry it and spread it after. The goal is not to pre germinate it.

There are also apparently PGS chemicals, as well as Biostimtiulants that can speed estabshment.

Curious, how did you accidently use KY-31 seed?


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## GuitsBoy (4 mo ago)

Green said:


> Sounds like you did everything right and have a good attitude and the right expectations. Keep us updated how this goes.


Thanks Green. I came across a number of suggestions when searching how to get rid of the stuff. My first thought was the PreM, though the gold standard is to glyphosate the whole yard, multiple times, and reno from scratch. The other option that pooped up from time to time was certainty as a selective tall fescue herbicide. There were a few threads on it, and a lot of people cautioning about using it. I'm hopefully it will work at reduced dosage since the grasslings are young and immature. Even if it does nuke the yard, it hopefully wont be as drastic as a glyphosate bath. Anyway, I do appreciate your very helpful tidbits here.



> Curious, how did you accidently use KY-31 seed?


I mentioned it in my original post, but basically it was a mixture of pure ignorance, amazon's search algorithm including "associated" items, and a delivery timed perfectly with a screaming three year old.

Here's the orginal post snippet:

Last year I overseeded KBG only, so this year I wanted to overseed a mixed seed again to introduce a bit more TTTF back into the lawn. In an effort to avoid the scotts/pennington coating tax, I searched for "kentucky bluegrass tall fescue seed" in amazon and was greeted by a number of choices. I picked a highly rated one, and read a few of the best and worst reviews, and pulled the trigger. It arrived while I was home alone with my 3 year old daughter, mid tantrum. I figured having her help me overseed the yard would be a nice way to occupy her for a bit. It wasn't until I was putting remaining 1/3 bag back into the garage that I noticed it made no mention of "bluegrass" only the words "kentucky 31 tall fescue". Here in suburban Long Island NY, K31 is a completely foreign animal, so like most people in the area, I'd never heard of it before. A quick google search later, I was violently nauseous, losing sleep for the next two nights worrying about how to address it.


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## GuitsBoy (4 mo ago)

So today is 12 days from application of the certainty. We had a TON of rain over the last week, remnants of H-Ian making it up the coast. And unfortunately with some family stuff to attend to, we'll be away this weekend. I had to make the decision to move up the plan by two days. I cut the lawn looooooow, then blanketed the whole thing with 4-5oz/Acre application rate of tenacity yesterday evening. Today I plan to rake out some topsoil to level, and do the actually seeding/overseeding. The KBG has been wet for 4.5 days, and even two days ago I saw little green sprouts in the slurry. Its been draining and drying indoors since last night, and I plan to mix about 7 lbs of seed with 32 lbs of milorganite to try to make it machine spreadable. I guess we'll see. 

So far, I dont see much damage being done to the existing tall fescue, nor the small KY31 grass seedlings. But Ive read the Certainty can take quite some time to do its thing. The grass has been stunted, but that could also be due to the colder weather these last couple weeks. I suspect Ill have to do a couple timed applications in the spring to get rid of whatever KY31 survives.


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## Green (Dec 24, 2017)

I think you're on the right track. Hopefully you have enough time for your seed to establish before it gets real cold. Tenacity right after the mow, plus topsoil, should make it really hard for that KY-31 to go through the Winter. It'll probably stop growing soon, and then start decomposing under the soil because now its growth is blocked by amino acid inhibition, chlorophyll inhibited (bleached), chopped in half, and put under soil. Most of it probably won't recover from all that. Just enough to be annoying might survive the Winter.


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## GuitsBoy (4 mo ago)

Thanks green. As best I can tell, none of the KY31 was tall enough to get cut. Most of the seedlings are in the 3/4 to 1 inch range, whether stunted from the certainty, or from the cooler weather. Unfortunately the topsoil was not a blanket over the whole yard, but only filling in a few depressions, and one area that puddles a bit with irrigation. Still, I'm hoping Ive done enough to hurt the bulk of the KY31 seeds, while still giving the KBG a fighting chance, even if it is an uphill battle at this late stage of the game.

Come spring, Ill continue hitting the lawn with certainty in addition to a preM in the hopes that it will continue to thin out any remaining KY31 or TTTF, and the KBG will spread and fill in. Even if I have to spot treat some clumps with glyphosate, that's fine. I just hope I dont have to nuke the whole thing.


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## Green (Dec 24, 2017)

Yeah, definitely reevaluate in Spring. I can tell you from experience, two apps of Certainty this time of year are almost guaranteed to destroy the KBG. Tried a few spots last year, and when Spring came, I was like, uh oh. It looked like Roundup had been sprayed. Quit while you're ahead.


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## ABC123 (Jul 14, 2017)

There’s nothing you can do besides put down dimension asap.


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## GuitsBoy (4 mo ago)

Update:

I'm one month from the accidental KY31 overseed. It's 17 days from the certainty application, 6 days from the tenacity application, and 5 days after pre-germinated KBG seeding.

The entire lawn has slowed down to a crawl, but I dont see much or any substantial damage to either the fescue or the existing KBG. The KY31 seedlings seem to be having a tough time though. I havent seen much if any appreciable growth in weeks. Some of the seedlings are an inch or just over, but most have petered out at about 3/4 inch height. I'm assuming the certainty is doing the trick because normally I would have expected the KY31 to have progressed further than it has after a full month. I'm just starting to see some bleaching from the tenacity application across the entire lawn. But aside from the nutsedge infestation, nothing looks dead-dead. Some of the existing tall fescue clumps have some brown blades, but they dont look to be dying exactly. They look as if they'll bounce back after a bit. I suppose that's fine, so long as the KY31's growth is stunted enough that it doesn't survive the winter. So far, the KY31 doesn't look dying, but it sure isn't growing either. 

I fully expect to have to blanket the lawn with certainty again in the spring, possibly two applications, with additional spot treatment of stubborn fescue clumps. I'm only seeing some very minor KBG germination at this point, so it will be an uphill battle for it to develop any root structure before winter. But one slight benefit is that it's competing against stunted grass.


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## Green (Dec 24, 2017)

GuitsBoy said:


> I fully expect to have to blanket the lawn with certainty again in the spring, possibly two applications, with additional spot treatment of stubborn fescue clumps. I'm only seeing some very minor KBG germination at this point, so it will be an uphill battle for it to develop any root structure before winter. But one slight benefit is that it's competing against stunted grass.


I didn't realize your goal was to get rid of all Fescue (even established TTTF). That is going to be a tall order. There used to be another herbicide in the same class as Certainty that supposedly was intended for this exact purpose, and did it better, but it went off the market, I think due to not being popular.

In any case, you have a real interesting experiment going, and it's interesting to read the updates. Please continue to update as things evolve.


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## GuitsBoy (4 mo ago)

Green said:


> I didn't realize your goal was to get rid of all Fescue (even established TTTF).


In all honestly, Its really not my primary goal. Killing the KY31 is primary. I expected some or all the established TTTF to be collateral damage, so in that respect, I dont mind getting ride of all the TTTF it thats what it takes to get the KY31 as well. It seemed simple enough to go to 100% KBG and then reintroduce TTTF in the following seasons, if at all. But ultimately, if some TTTF survives, I wont mind. But I do also have some wide bladed ugly clumping fescue as well, which may actually be KY31 or something similar from the previous owners. Those clumps I'd like to get rid of for sure. Ill spot treat with the certainty, and if no luck, then Ill hit the clumps with roundup. As long as I dont have to do a full reno, Ill be relieved.

I believe the herbicide was TFC (Chlorsulfuron) tall fescue control. As I understand it, its actually illegal these days, at least for home lawn use. Sounds like it would have been a good option though.

But as an update, the KBG continues to germinate and quickly pop up. A few blades that had just sprouted two days ago, are now almost 2 inches in height, far surpassing the KY31 seedlings already. That gives me some hope. Seems like more seed is germinating every time I step outside to look.


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## Green (Dec 24, 2017)

@GuitsBoy

That sounds like it's going well. Yes, Chlorsulfuron. There was a brand called Corsair or something. It was marketed to take Fescue out of KBG, I believe. I never looked into a lot of the details. But there are a lot of Sulfonylurea herbicides. Many are only used in warm season turf. At least one can kill trees if applied too heavily, or drifts. They are apparently a quirky category to say the least. Sulfosulfuron is sort a fence-dweller. It can be used in cool season, carefully, but typically is not.

I would follow the gist of this label next Spring: https://atticusllc.com/wp-content/uploads/2020/08/Sertay-Specimen.pdf
It has cool season lawns (KBG) listed on it. However, I would not ever go above 0.5 oz per acre on KBG.

I would spot treat anything you don't want with glyphosate next Spring. Don't even mess around trying anything else on the small spots. It works. Three apps with a small amount of AMS and the NIS. Maybe citric acid, too. I can give you the recipe I got from people on here.

I bet the pre soaking is going to save you. Not just due to time. But it also gave the KBG a head start versus any residual herbicide.


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## GuitsBoy (4 mo ago)

I'm still in the sprout and pout phase with the KBG seedlings, praying for a warm November. We had some cold weather, which I'm sure you experienced up in CT as well. More mild temps have returned, and the grass seems to be growing again, however the KY31 seems to be growing again as well. If the KBG finally looks to have taken hold well enough, I'm considering another treatment of certainty right around thanksgiving before the grass goes dormant. Weather depending, or course. I see some of the pre existing ugly clumps of TF are really hurting, and I'd love to finish them off, as well as inflict further injury on the KY31 seedlings, which are still not at a mow-able height six weeks after the erroneous seeding. I think I can manage to avoid spraying certainty on the few bare patches where the new KBG is growing to give them a better chance of survival, yet still knocking out as much of the KY31 as possible. All the other areas I can probably just let the KBG fill in via rhizome action, perhaps with a small nitrogen blitz come early spring.

Perhaps I should start spoon feeding the lawn ahead of time, to ward off damage from the certainty application later in the fall? But I also dont want to strengthen the KY31 seedlings either. But then again, I did put down a bit of slow release nitrogen earlier in the fall, maybe Ill just sit tight.


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## Jersey_diy (Sep 5, 2020)

Good luck to you...I applied certainty to my lawn and smoked it completely with no time left to grow grass again. Went the whole winter with a dirt patch. I am rooting for you though!


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## GuitsBoy (4 mo ago)

Jersey_diy said:


> Good luck to you...I applied certainty to my lawn and smoked it completely with no time left to grow grass again. Went the whole winter with a dirt patch. I am rooting for you though!


Thanks Jersey_diy. I applied at a low dosage, around .37 oz per acre. If anything, it wasn't effective enough. But the many cautionary tales, such as your own, made me very careful about not being to heavy handed with it. Sorry to hear about the hardship, but thank you for putting the info out there.


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## Jersey_diy (Sep 5, 2020)

GuitsBoy said:


> Thanks Jersey_diy. I applied at a low dosage, around .37 oz per acre. If anything, it wasn't effective enough. But the many cautionary tales, such as your own, made me very careful about not being to heavy handed with it. Sorry to hear about the hardship, but thank you for putting the info out there.


Thanks, it gave me the opportunity to learn that I could reseed in spring and survive a drought filled summer.... of course with a lot of irrigation. 

Don't forget to keep us updated


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## Tungsten (6 mo ago)

How much KY31 is there at this point? I think I saw that your lawn is 4000 sq ft. Do you think you could hand-pull the remaining KY31? If so, then you wouldn’t need to worry about Certainty possibly damaging your good grass. I wish you success with whatever approach you take


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## GuitsBoy (4 mo ago)

Tungsten said:


> How much KY31 is there at this point? I think I saw that your lawn is 4000 sq ft. Do you think you could hand-pull the remaining KY31? If so, then you wouldn’t need to worry about Certainty possibly damaging your good grass. I wish you success with whatever approach you take


Thanks, Tungsten. I have no idea how to answer that, unfortunately. I used the spreader to overseed about 13 or 14 lbs of KY31 throughout the 4K sq ft. I assume it would be a nightmare to comb through the established turf to look for KY31 seedlings, not to mention the seedings dont look all that different from the KBG yet. I have some small sections where I had KY31 coming up, and Ive kept an eye on those areas to gauge how it's doing/dying. The KY31 is still mostly just single shoots with maybe a few starting to bunch slightly, but it's still very thin bladed, and somewhat boat shaped. Perhaps next year, it would be easier to pick out any clumps, or more likely just hit them with a laser shot of glyphosate and reseed or wait for the KBG to grow in.

But if I hit the lawn with another low dose .37 oz / acre shot of certainty, I have little doubt that the established turf will survive just fine. The good lawn is really starting to rebound from the back to back certainty and tenacity treatments, but some of the established coarse fescue still looks very close to death. I'd really like to finish the job.


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## Green (Dec 24, 2017)

This is getting intense.

I feel like I'd be worried about the KBG seedlings being destroyed if spraying again at this point. If I did spray again, I'd go for an even lower rate (0.25) personally. I should look up what I did in the past that resulted in dead spots of established grass, so you can maybe avoid that degree of damage.

Yeah, same weather pattern here. Finally it's like October and not November. Even a bit of September mixed in.


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## Green (Dec 24, 2017)

Looks like I mixed at the 0.50 oz rate and then spot sprayed that at least twice last Fall. Some spots may have gotten a third app, but I don't know for sure. I ended up with essentially dead spots over the Winter/early Spring.

I'm not sure what to tell you at this point, other than, try to figure out if the KY-31 seedlings actually grew in the last two weeks or so. If they're stuck at the same height since then, I think you're good (that it's working well) and don't need to think about another app.


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## GuitsBoy (4 mo ago)

Thanks Green. The KY31 seedlings are indeed growing again, however at a very slow pace. Theyre still below a 2.5" HOC at six weeks after seed down. I'd believe they would normally be much further along. But the fact theyre still growing is bothersome. 

I do fully understand another certainty application puts any new KBG seedlings at considerable risk, but in all but a few bare spots, the risk seems perfectly acceptable, since the existing lawn is thick enough to fill in with normal KBG spreading / nitrogen. In that case, it becomes ".375 ounces of prevention equals a pound of cure". Better to nuke the KY31 now at the expense of wasted KBG seed than to let the KY31 mature and be far more difficult to eradicate next season.

No matter what, I think I'm well ahead of the game, compared to doing nothing. Thanks again.


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## GuitsBoy (4 mo ago)

Another quick update: Lawn is looking really good lately. Thin spots are filling in, though not much top growth from the new KBG. New grass is all in the 1 to 1-1/2 inch range, but it is thickening. I do see that a number of KY31 seedlings have survived the certainty and tenacity treatments. But these are relatively few, and I think I can spot treat them in the spring. While the warm weather was still here, I was contemplating another certainty treatment before winter, but now that the temps have plummeted back to where they belong, I think I'll hold off. The KBG seedlings didn't look mature enough to survive, but who knows. Instead, the day before the recent cold snap, I put down 1 to 1.25 lbs/K of mixed fast and slow nitrogen in the hopes it would go right towards root development and storage in these colder temps. I'm hoping the KBG seedlings dont get nitrogen burn, but I think the weather is with me. 

I've been watering three times daily since the overseed, but after hitting 28 degrees last night, I think its time to blow out the lines for the year and call it a wrap. In early spring, I'll put down a 3 month rate of prodiamine, and wait for greenup. If the KY31 appears to green up before the KBG, I might try another blanket treatment of certainty, followed by spot treatments of any obvious clumps with certainty or even glyphosate depending on the size. Once the KBG greens, I'll start spoon feeding and gradually push it to fill in any gaps before the summer heat. But at this point, I think I'm done with seeding, and can manage the rest with regular feeding.

Looking back, I wish I went a little heavier on the initial Certainty application. Or perhaps the rain later that night might have reduced its effectiveness. Either way, it definitely seems to have helped since the lawn is not yet overrun with KY31, and I think there's a good chance I can spot treat the rest. So far, I'm still calling it a qualified success.


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## Green (Dec 24, 2017)

Sounds like a success. Why not pull out some of the stuff you don't want this season as you see it if there isn't much? Or is it too blended and not practical to separate at this point?

Let's see what happens in the Spring, too. Looking forward to hearing.


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## GuitsBoy (4 mo ago)

Green said:


> Why not pull out some of the stuff you don't want this season as you see it if there isn't much? Or is it too blended and not practical to separate at this point?


Its pretty well woven in, and a lot of the young KY31 is difficult to differentiate from the KBG. I pick them out when I come across them, but it wouldnt be easy to canvas the entire lawn that way. 

I'm thinking in the spring, Ill be able to pick out the clumps more easily, as it either greens up sooner, or matures as a lighter lime green. If its really not that bad, I might just leave it and only treat them if they develop into big and ugly clumps. But yes, so far I'd have to guess that a large percentage of the KY31 has been prevented.

Thanks again for your help!


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## Green (Dec 24, 2017)

@GuitsBoy

I can only imagine how many you'd have if you allowed it to grow normally. Thousands of plants. If you get down to hundreds, I'd call it successful.

I once spent many, many hours over a couple of years pulling out Timothy grass plants from supposed weed free straw, mostly in my back reno. Probably pulled 2,000 plants in the first few years. I still get one or two occasionally, years later.

If they sold KBG or TTTF straw, this would be a non-issue for most, but I digress. No more straw.


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