# Spring Pre-M strategy for areas with spot-renos?



## Green (Dec 24, 2017)

I've always used granular Dimension for Spring Pre-M. I like Dimension because it works well against crabgrass and many Summer annual weeds, but doesn't have the super long residual of Barricade (which I've used in the late Summer in granular form against Poa annua).

There are still some spots (Poa Trivialis) in the front lawn that I need to glyphosate early in the Spring, and then replace with seed (or sod that I'll grow from seed). It's really hard to find consistent information on this topic, but the most reasonable info I've seen indicates that you don't want to Pre-M over new sod for at least 2 months because it will inhibit the roots from getting deep enough before Summer (is this really true?).

So, the solution I thought of (no pun intended) is to spray the pre-M instead of laying down granular. That way I can control where it's going and skip over the glyphosated spots that will need to be redone with new grass.

My questions:

-Does this all sound logical? is there another solution I'm not thinking of that's easier?

-What Dimension product for spray application is the most affordable, and how long will it last in storage? I saw generic Dithiopyr 40WP. That was the least expensive one I saw. Any other Dithiopyr products for spray application that I should be looking at? I'm set on using Dithiopyr because I've been using it for years in granular form, and know how it behaves.

-How do the application rates for the liquid mixes equate to those of a granular? For reference, I apply 4 lbs per thousand sq. feet of 0.15% granular Dimension at Forsythia bloom. I'd like to apply whatever rate of the liquid mix that will put down the same amount of AI per area.


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## bernstem (Jan 16, 2018)

Generally you want to avoid traditional pre-emergents (e.g. Dimension, Barricade, etc.) when seeding or sodding. It doesn't matter if you spray or use granular, both forms will inhibit seed or sod establishment.

What you want is Mesotrione (Brand name Tenacity or some formulations of scott's starter fert) which will provide ~30 days of pre-emergent control of many weeds without inhibiting sod or seed establishment. You can apply that to areas needing seed or sod at 4 Oz/Acre every 30 days until the new seed or sod is established. Once established, you can then move to Barricade or Dimension. Mesotrione also has the added benefit of temporarily bleaching Poa Trivialis which makes it easier to target.


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## high leverage (Jun 11, 2017)

Traditional Pre emergents are notorious root pruners. Skip Prodiamine, Dithiopyr, Pendimethalin, and Indaziflam if root development is important. Use something like what bernstem suggested above or something like Isoxaben although it does nothing for grassy weeds only broadleaf. Only use after seedlings are established (three leaf stage and tillering) and well rooted.


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## gene_stl (Oct 29, 2017)

http://turf.wisc.edu/wp-content/uploads/2013/05/Herbicides-safe-on-seedlings-Reicher-2013.pdf


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## Pete1313 (May 3, 2017)

Green said:


> -What Dimension product for spray application is the most affordable, and how long will it last in storage? I saw generic Dithiopyr 40WP. That was the least expensive one I saw. Any other Dithiopyr products for spray application that I should be looking at? I'm set on using Dithiopyr because I've been using it for years in granular form, and know how it behaves.
> 
> -How do the application rates for the liquid mixes equate to those of a granular? For reference, I apply 4 lbs per thousand sq. feet of 0.15% granular Dimension at Forsythia bloom. I'd like to apply whatever rate of the liquid mix that will put down the same amount of AI per area.


If my math is correct, you will need .24 oz of Dithiopyr 40WP to get the same amount of active ingredient as 4 lbs of Dimension .15%.

Dithiopyr 
.24oz×.4(% of ai)=.096oz of ai/1000 sq ft

Dimension .15%
64oz(4lbs)×.0015(% of ai)=.096oz of ai/1000 sq ft

Both will give you a rate of 4.18 oz(.261 lbs) of ai/acre.


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## Ware (Jan 28, 2017)

bernstem said:


> Generally...


Welcome to TLF, bernstem!


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## Green (Dec 24, 2017)

I would argue liquid app versus granular does matter in my case...

With liquid, I could just spray up to, but avoiding, the specific sodded areas...in theory. I've never used liquid dithiopyr, but I don't see why this wouldn't be the case.

Is this sound logic?

Granular...you can't easily control where it goes.


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## Green (Dec 24, 2017)

Pete1313 said:


> Dithiopyr
> .24oz×.4(% of ai)=.096oz of ai/1000 sq ft
> 
> Dimension .15%
> ...


I'm going to have to look at this and try to duplicate it myself...thanks.


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## g-man (Jun 15, 2017)

Green and Bernstem, Welcome to TLF

My opinion (and I what I have done in the past for quackgrass) is:

1) Apply PreM in March. 
2) Kill with Roundup
3) Remove the dead stuff and let the KBG fill in

If I had a larger area, I would avoid doing this in spring, but if I had to I would still the same steps. I would try to avoid the area with PreM (but not 100% possible). I would let a couple of good rains/irrigation/time to ensure the PreM is absorbed by the soil. I would then remove 2in of the soil after the kill and replace it with new topsoil.


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## Green (Dec 24, 2017)

bernstem said:


> What you want is Mesotrione (Brand name Tenacity or some formulations of scott's starter fert) which will provide ~30 days of pre-emergent control of many weeds without inhibiting sod or seed establishment. You can apply that to areas needing seed or sod at 4 Oz/Acre every 30 days until the new seed or sod is established.





high leverage said:


> Traditional Pre emergents are notorious root pruners. Skip Prodiamine, Dithiopyr, Pendimethalin, and Indaziflam if root development is important. Use something like what bernstem suggested above or something like Isoxaben although it does nothing for grassy weeds only broadleaf. Only use after seedlings are established (three leaf stage and tillering) and well rooted.


Bernstem and high leverage,

I'm actually considering this option, since I have the Mesotrione already. The only thing I'm not sure of, is how long it would take sod to root adequately to use a "real" pre-M. I've heard up to 3 months, but I wonder if it really takes that long. I remember seeing studies where researchers applied Dimension to recently seeded (less than 2 months post germination) cool-season grass. Since sod is more mature than seed, you would think that if anything, it should be able to root sooner than seed.

I had really good luck this past Fall growing my own sod in trays.


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## Green (Dec 24, 2017)

g-man said:


> Green and Bernstem, Welcome to TLF
> 
> My opinion (and I what I have done in the past for quackgrass) is:
> 
> ...


Hi g-man...thanks.

If I had only KBG, I might do that if I could deal with bare spots for a while. But I redid the lawn this past Fall (heavy overseed after using Velocity during the Summer), and I'm just going after the remaining spots that didn't get killed. Since it's a nice TTTF/KBG mix now (with 5% PR), I plan to replace the spots with the exact same mixture. That's why I'm planning to grow sod again.

I am hoping the Triv will be green enough in March to kill, before the other grass...to minimize collateral damage.

Right now, I have a bunch of brown spots from mid-Fall Tenacity (and some due to people walking on the lawn during the Winter), so I can easily keep an eye on it as it greens up in March.


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## Green (Dec 24, 2017)

gene_stl said:


> http://turf.wisc.edu/wp-content/uploads/2013/05/Herbicides-safe-on-seedlings-Reicher-2013.pdf


That link says Dimension can be used after 1 or 2 Mesotrione apps. So, there's some subjectivity there. 1 app would be the 6-week point, though. That might be mid-May, if everything works according to schedule in terms of seed germination.

Anyone strongly advise against using Dimension as soon as 6 weeks after laying sod pieces based on experience?


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## g-man (Jun 15, 2017)

The label says 2 mowings for seeding. For sod it says rooted and filled in. Irrigation and sun and temperature would affect how long for roots to really take hold.


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## bernstem (Jan 16, 2018)

I would go 2 months for sod establishment which would be 2-3 Tenacity applications. Another good rule of thumb is 2-3 mowing. There is data that you can transition to Dimension earlier, but I don't see a need to push it (I also do not have any direct experience with early dimension after seeding or sodding). Tenacity will control almost all the weeds that are likely to be problematic (except Poa Triv). You could just use Tenacity on the entire yard until the sod is established and reduce your Poa Annua population (I'm guessing you have at least some), though I would consider a traditional pre-emergent in areas that don't need repair . A sprayed application will allow better control over the border. As for dosing, the liquid formulation will give you dosing so you don't need to worry about converting AI (active ingredient) of granular to AI of liquid. Doing that conversion is just way too much work.

The data I have seen on root development in established cool season turf is not at all clear how much root pruning happens. Last time I looked into it, the consensus seemed to be that there was some, but not enough to matter. I can tell you I have seen my KBG fill a 6-12 inch hole in a season even with two applications of Barricade providing a nearly season long barrier. That is without doing anything to explicitly encourage spreading such as frequent Nitrogen and water. Certainly if you are looking for maximal root development, you would skip the pre-emergent, but in the grand scheme of things that promote and maintain healthy roots, other factors such as soil quality, soil tilth, macro/micro nutrient levels, appropriate watering and mowing and disease management are likely much more important.


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## Green (Dec 24, 2017)

I think I'm going to go with the Tenacity for the first 6-8 weeks, since I have it. I'll have to play it by ear and see how long it takes to grow the sod, and then for it to root fully once transplanted. The Tenacity will also allow any potential lingering grass seeds from the Fall to germinate, and will allow me more time to glyphosate (and redo) any new spots that I see in April that I might have missed on the first round in March. If I used a conventional pre-M too early, I would have to dig up the soil.

Tenacity will also prevent any potential Poa annua seeds from growing, as mentioned in a previous post. I haven't seen any Poa annua in that lawn area for over a year, but there could very well still be seeds there.


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## pennstater2005 (Jul 17, 2017)

Ware said:


> bernstem said:
> 
> 
> > Generally...
> ...


Just seeing this and ditto....nice to see more familiar names


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