Thanks for your question.  I've looked at your question history with our forum.  It would appear that you and bentgrass have had a long association!!  I can understand your frustration.  Before giving you my best shot as an answer for your recent question, I need a little more information from you.

1).  Past Master Gardeners have suggested that perhaps you have a crabgrass problem rather than a bent grass problem.  What is your thinking about this?  Have you tried any procedures directed towards the elimination of crabgrass?  If so, any success?

2).  In September 2023, it was recommended that you remove the top layer of turf and over seed with some other grass.  If you did you do this, what was the end result both last fall (2023) and this spring (2024)?  Any improvement?

3).  It would appear that the first timeTenacity was applied was last fall (2023) by your lawn service.  Correct?  Do you have any idea as to the number applications done last fall and if more than one, what were the time intervals between applications?

4).  Tenacity can also be used as a pre- emergent herbicide in early spring.  Have you ever tried Tenacity or any other pre-emergent herbicide in the spring.

5).  What's your best guess as to how long you have been having an issue with bentgrass.

Looking forward to your response.  Thanks for consulting with us.

Good morning.

It looks as if you attempted to send a response to our forum last evening.  Unfortunately, nothing was received on our end.  If we are mistaken in this, our apologies.

Thanks for your question. I've looked at your question history with our forum. It would appear that you and bentgrass have had a long association!! I can understand your frustration. Before giving you my best shot as an answer for your recent question, I need a little more information from you.

1). Past Master Gardeners have suggested that perhaps you have a crabgrass problem rather than a bent grass problem. What is your thinking about this? Have you tried any procedures directed towards the elimination of crabgrass? If so, any success? We always use a pre emergent for crab grass, and it never seems bad. Sometimes a few little patches here and there, but I then just spray those small patches. We did have many patches of quack grass ( I believe that what it was) I used round up on that last fall. Still waiting to see it any comes back I have a neighbor that doesn’t care about his lawn.

2). In September 2023, it was recommended that you remove the top layer of turf and over seed with some other grass. If you did you do this, what was the end result both last fall (2023) and this spring (2024)? Any improvement? We scalped the dead areas and they did bring in dirt and seed

3). It would appear that the first timeTenacity was applied was last fall (2023) by your lawn service. Correct? Do you have any idea as to the number applications done last fall and if more than one, what were the time intervals between applications? 3 times total, and 2 weeks in between

4). Tenacity can also be used as a pre- emergent herbicide in early spring. Have you ever tried Tenacity or any other pre-emergent herbicide in the spring. Only for crabgrass. No, tenacity- didn’t know I could. Things were looking great this spring, (I thought) I was just trying to fill in some bare spots with dirt and seed in a few places, as I raked I noticed the bentgrass. Did not think we had as much as we did—until they sprayed and I watched it turn color. They have sprayed twice so far. It was three weeks apart because of all the rain. He is due to come back on Wednesday for the 3^rd.

5). What's your best guess as to how long you have been having an issue with bentgrass. As I think back, quite awhile! I never knew what it was just knew it was different grass, and I hated it. Sometimes looked more brown than other times, and when I would rake it, whole patches would come up like all together. We installed an irrigation system 3 years ago, I am guessing it just took off even more since then

Looking forward to your response. Thanks for consulting with us.

Thank you I don’t want to give up, but feeling defeated. I even found a patch of it in our side yard , and I believe one in the front as well. Those are new.

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Good morning.  Thanks for your response.  I would like to clarify a few things as I develop a remedial plan for your situation.

1).  Do you know the name of the pre-emergent that was applied for the crabgrass?

2.  You indicated that in fall 2023, Round-Up was used to kill the quack grass.  Have you ever tried using Round-Up for the bent grass?  Perhaps the bent grass is too integrated with your regular grass that you can't use it?

3).  When you did the scalping and brought in dirt, last fall (2023), was this to cover the areas where the bent grass had been?  Perhaps it was to deal with both areas of quack grass and bent grass?

4).  What kind of grass seed was used last fall and how did these scalped and seeded areas look this spring?

5).  You indicated that spraying of Tenacity has been done twice so far in 2024 with a third application yet to be done.  Has spraying of Tenacity for the bent grass ever been done in late summer/early fall?  I ask since that is the best time to use Tenacity against bent grass and not in July.  I assume that the current spraying of Tenacity is at the suggestion of your lawn care service.  If so, I'm curious as to why they're doing it now and not at the recommended time!

I apologize for all my questions.  I am endeavoring to provide you with a course of action that might be effective.  Since you have been dealing with bent grass for several seasons, previous courses of action do not appear to have been completely satisfactory.

Thanks so much for your patience and your information.  

I'm sorry but nothing came through with your last posting.

Thanks for your persistence

1). Do you know the name of the pre-emergent that was applied for the crabgrass? Just whatever we get at Menards – we have always done our own yard maintenance- just needed help identifying and killing the bentgrass

2. You indicated that in fall 2023, Round-Up was used to kill the quack grass. Have you ever tried using Round-Up for the bent grass? Perhaps the bent grass is too integrated with your regular grass that you can't use it? He didn’t even suggest it, and it would have killed a lot of good grass too.

3). When you did the scalping and brought in dirt, last fall (2023), was this to cover the areas where the bent grass had been? Yes Perhaps it was to deal with both areas of quack grass and bent grass? Yes both areas

4). What kind of grass seed was used last fall and how did these scalped and seeded areas look this spring? I believe they used a 50/50 or 70/30 Blue/Rye Lots of bare areas in the fall as we were pretty late to seed, and had very heavy rains afterwards too. But, the spring looked great-and filled in most areas. Some of our more shady areas were a little bare, but overall I was pleasantly surprised….. until I noticed the bentgrass

5). You indicated that spraying of Tenacity has been done twice so far in 2024 with a third application yet to be done. Has spraying of Tenacity for the bent grass ever been done in late summer/early fall? I ask since that is the best time to use Tenacity against bent grass and not in July. Last year it was around August 18^th we started

I assume that the current spraying of Tenacity is at the suggestion of your lawn care service. Well sort of…. As soon as I noticed it I called. My thinking was to get it before it continued to spread. Thought he would spray once, and when we saw how much turned white we could go from there. Hoping it wasn’t much, and we could kill it off and then naturally the good grass would fill in. Thought we would aerate again and overseed a couple weeks after the last spray and pulled out the dead stuff.

If so, I'm curious as to why they're doing it now and not at the recommended time! Great question if they shouldn’t be. It was VERY difficult to even find a company to do it last year. Finally found a company that would send out their “ Turf Guy”, and he identified it, and came up with the plan. I was actually the first homeowner they had worked with,,,, I know I was a Guinea pig!!! He is no longer there,- he was let go……. so the person that does the actually spraying has been researching it and working with me. I believe I asked here once for a name to help, and was told you can’t recommend anyone, so this person and company is all I have to physically see it and help.

I apologize for all my questions. I am endeavoring to provide you with a course of action that might be effective. Since you have been dealing with bent grass for several seasons, previous courses of action do not appear to have been completely satisfactory. No need for you to apologize, I want the help and with what we already invested I don’t want to give up…unless I have to. I wish we could get a Turf expert here with a solution once and for all.

Thanks so much for your patience and your information. THANK YOU!

Thanks for getting back to me. I think that I am getting a better understanding of your situation.

Look at the following website. This comes directly from the instructions for the use of Tenacity. It can be used both as a pre-emergent herbicide and a post emergent herbicide. Its active ingredient is a compound known as Mesotrione. This compound inhibits the production of chlorophyll. This is how it kills certain plants. Of the various types of grasses, bent grass is very sensitive to Mesotrione. Blue grass and fescues are relatively insensitive to it. The best times to apply Tenacity are when bent grass shoots are emerging from the soil (pre-emergent use), or when bent grass is spreading (late summer to early fall; post-emergent use). The label on Tenacity cautions that it should NOT be applied during times of drought (mid-summer). This is why I was surprised that it is now being applied (late July, early August). Tenacity simply may not be effective against bent grass at this time of the season.

More will be forthcoming. At this point, please read this site so that you are familiar with the product that is being sprayed around your yard. I suspect that you will end up knowing more about its use and bent grass than your lawn service!!

https://labelsds.com/images/user_uploads/Tenacity Label 2-1-09.pdf

Thanks again for your patience.

With respect to your bent grass situation, here are my suggestions:

1). Although it may seem like a step backwards, I believe it is a good first step. The Turfgrass Diagnostic Laboratory at the University of Wisconsin is known for its expertise in dealing with turf problems. I would suggest that you submit some samples of your turf to them. One should consist of what you believe is crabgrass and the other should be of what you think is bent grass. It is important that you can distinguish between these two. Please contact them ahead of time regarding submission of samples. Also in your initial contact, mention that you need to know the best way to deal with these two types of grasses.  There will be q nominal fee for their services. See:

https://tdl.wisc.edu/

2). The most often used herbicide intended to kill creeping bent grass is Tenacity. It can function as either a pre-emergent or a post-emergent herbicide. Its active ingredient is a compound known as mesotrione, which is derived from a naturally occurring compound produced by the bottlebrush plant (Callistemon citrinus). Its mode of action is to inhibit photosynthesis in susceptible plant species.This is how it kills certain plants. Of the various types of grasses, bent grass and crab grass are very sensitive to Mesotrione. Blue grass,  rye, and fescues are relatively insensitive to it. As a post-emergent herbicide, it is most effective when applied in late summer to early fall. Multiple applications are typically needed. In your question you expressed some disappointment in your fall 2023 experience with Tenacity.  I suspect that either it was applied at the wrong time and/or only a single application was made. Look at the following website. This comes directly from the instructions for the use of Tenacity.  The best times to apply Tenacity are when bent grass shoots are emerging from the soil (pre-emergent use), or when bent grass is spreading (late summer to early fall; post-emergent use). The label on Tenacity cautions that it should NOT be applied during times of drought (mid-summer). This is why I was surprised that it is now being applied (late July, early August). Tenacity simply may not be effective against bent grass at this time of the season. See the following for a recommended protocol:

https://greenhow.com/pest-control-blog/what-is-tenacity-weed-control-does-tenacity-kill-bentgrass/

Going forward, these are my suggestions starting August 2024:

1. Although it is not the opportune time, complete the Tenacity treatment that you are now doing.

2. If you get a report back from the Turfgrass Diagnostic Laboratory, identify small to medium sized areas of yard in which you want to eliminate the bent grass. In mid-August (2024) scalp these areas, roughen the underlying surface, and reseed. I would avoid using seed containing perennial rye. It can be subject to winter kill. Rather, use a seed mixture consisting of 50% bluegrass by weight and 50% fescue by weight. Since bluegrass seed is smaller than fescue seed, you will end up by applying more bluegrass seed than fescue seed. Here are the fescues you should consider:

https://turf.umn.edu/news/finding-right-grass-seed

https://extension.umn.edu/lawn-care/seeding-and-sodding-home-lawns

In this next site, note the comments about perennial ryegrass:

https://turf.umn.edu/news/eric-watkins-turfgrasses-minnesota-lawns

3). Water things very well to the extent of at least 1 inch of water per week.

4). In mid-September 2024, apply a winter fertilizer to your entire yard. These contain a slow-release form of nitrogen (look for “urea” on the product label). This will slowly feed your turf this fall and continuing into winter. See:

https://extension.umn.edu/lawn-care/seeding-and-sodding-home-lawns

https://www.thisoldhouse.com/lawns/reviews/winter-fertilizer

As a Master Gardener of the University of Minnesota, I cannot endorse any commercial product. For this reason consider the fertilizer mentioned in the follow as one of many possible winter lawn fertilizers:

https://www.amazon.com/Scotts-Turf-Builder-Lawn-Food/dp/B000I1M5OU/ref=asc_df_B000I1M5OU/?tag=hyprod-20&linkCode=df0&hvadid=<personal data hidden>3&hvpos=&hvnetw=g&hvrand=<personal data hidden>77573164&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9019787&hvtargid=pla<personal data hidden>34&mcid=606dff94896c3b5290a34b7819a48939&gad_source=1&th=1

5). In mid-April 2025, start a Tenacity protocol intended as a pre-emergent treatment against both bent grass seed and crab grass seed. Both types of these seeds germinate in the spring. By using Tenacity, you will be trying to inhibit this germination. Be sure to apply this herbicide according to its product label. First treatment should begin around mid-April (2025); second treatment around the first of May; third treatment around mid-May. See:

https://www.greencastonline.com/techarticle.aspx?gcaid=198419 - :~:text=When applied just prior to,tank for seeding large areas.

6). In early June 2025, apply a weed and feed fertilizer according to directions on the label.

7). Unless things look terrible, hold off on any spring grass planting.

8). Don’t apply any fertilizer or Tenacity during summer 2025.

9). In mid-August 2025, start Tenacity treatments again. First application mid-August 2025; second treatment towards the end of August; third treatment mid-September. In addition bent grass, this treatment will also kill crab grass before it goes to seed. See:

https://extension.psu.edu/postemergence-control-of-crabgrass-and-other-summer-annual-grasses-in-lawns - :~:text=Mesotrione (Tenacity) is a systemic,nimblewill, and nutsedge in turf.

Dealing with turf issues is an adventure. I have confidence in the procedures I’ve outlined. However, if at any time issues arise, and/or you have questions about the steps I’ve outlined, please get back to us. I will keep monitoring things and if any future questions are directed towards another Master Gardener, I will see that they get reassigned to me.

Good luck and especially thanks for your exceptional patience.

Thanks for your response.

1). Thanks for your comments regarding crab grass and quack grass. It was never clear to me which one, or both, were issues. Deal with the quack grass as per your past practice.

2). With respect to reseeding, you are the best judge of this. Do as little or as much as you see fit.

3). The aeration is not necessary since you will be bringing in some dirt. It wouldn't hurt to do this in fall 2025.

4). Over seeding the entire yard would be great if you wanted to expend the effort. A cautionary note. If you go with a bluegrass/fescue mixture, be aware that these two grasses have slightly different appearances. To minimize the final visual effect be sure to thoroughly mix the seeds before seeding.

5). I did a brief goggle search on different forms of Mesotrione.  Here’s what I came up with:

a).  Tenacity: This is one of the most popular herbicides containing Mesotrione, primarily available in a liquid formulation but sometimes available as a granular product.

b). Callisto: Another product containing Mesotrione, primarily in liquid form but some formulations may come as granules.

c).  Acuron: This herbicide combines Mesotrione with other active ingredients and is usually available in liquid form, though some granular options might exist.

d).  Lumax EZ:  This is a pre-emergence herbicide that contains Mesotrione along with other active ingredients and is available in liquid and granular forms.

e).  Zemax: Similar to Lumax EZ, it contains Mesotrione and is available in liquid and granular forms.

Whatever product you select, be sure that on the product label it indicates it is effective against bent grass.

Onward!.  Thanks for consulting our forum.  Good luck.

Thanks for your last response.

Before addressing your two questions, let me repeat a point that I’ve made before. In reviewing all the correspondence that has transpired since your original question, I’m troubled by the fact that the grass in question (i.e., bent grass) has not yet been completely identified to the total exclusion of all other possibilities. Specifically, the following four grasses are all very similar in appearance:

1). Creeping bent grass

2). Tall Fescue

3). Crabgrass

4). Quack grass

Using just pictures, an unambiguous differentiation among them is not easy. My concern is that my suggestions are all based upon the assumption that creeping bent grass is correct. If this is not a correct identification, then time and money may be wasted. I previously suggested that a first step in dealing with your situation was to submit grass samples to the Turfgrass Diagnostic Laboratory at the University of Wisconsin. It is true that this would involve some expense and effort. Nevertheless, it may be the most efficient way of being sure we are on the right track.

With respect to your two questions:

1). No harm would be done by a fourth Tenacity treatment. I assume your mention of a light raking meant a raking before the Tenacity treatment. This would be OK as it might expose some hidden bent grass to the Tenacity. Possibly a bamboo rake might be better than a metal rake?

2). With respect to the application date for the winter fertilizer, it is critical that this be done before the ground is frozen. This will ensure that some of the fertilizer is taken up by your turf before winter sets in. Putting fertilizer put on frozen ground will just sit there and not enter the grass. For the Metro Area, the average date of first frost is between October 1^st and October 10^th. When you previously applied winter fertilizer in early November, I question how much of the fertilizer nutrients entered the grass due to frozen ground. When I suggested application in mid-September, this would be about two to three weeks before the average first frost. See:

https://extension.umn.edu/planting-and-growing-guides/lawn-care-calendar

https://yardguardmn.com/fall-fertilizing/

https://www.kglandscape.com/how-often-fertilize-lawn

https://lawn.pro/blog/calendar-lawn-care-minnesota

Two final points:

1). If you do a fourth Tenacity treatment, do that a few days before applying the winter fertilizer. Tenacity is most effective against growing bent grass. To the extent that the winter fertilizer stimulates bent grass growth, the Tenacity will be there waiting for that to happen.

2). It sounds that in the past, you raked up all the leaves from the yard. I would suggest for this fall (2024), you don’t do that. Unless you already have one, get a mulching blade installed on your power mower. Installation is also a relatively easy DIY project. This type of blade should be available at any hardware or gardening center. Essentially, a mulching blade consists of two separate mowing blades, one on top of the other. Two blades means that things essentially get mowed twice. Use this blade for your leaves and leave the leaf debris on the lawn. Do this after you have applied the winter fertilizer, perhaps in mid-October. This leaf debris will consist of very small leaf pieces. I grant you that this may create a slightly untidy look to things. This would only be temporary as this debris will work its way into the soil and mix with the previously applied winter fertilizer. It is also an excellent way to provide organic matter to your turf. By spring 2025, your lawn should return to its normal appearance. See:

https://turf.umn.edu/news/do-you-really-need-rake-all-your-leaves-update

https://www.twincities.com/2019/11/08/mulch-mow-bag-leaves-fall-yard-cleanup-fertilizer/

Much material to digest! Feel free to ask any additional, related questions. Good luck.