# Princep Simazine Pre-Emergent Protection Timing



## UltimateLawn (Sep 25, 2020)

Anyone know at what rates Princep (Simazine) will provide pre-emergent protection?

Per the label, Prodiamine 65 WDG gives 3 months of protection @ .5 lbs/acre.

I think that Specticle provides one month for each 1 floz / acre for the typical weed control. (see below for both).


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## Bombers (Jul 14, 2020)

Can you post the study where these charts came from? I'm interested in reading the whole thing.

Also, I believe simazine has a shorter half-life than most preM.
http://extoxnet.orst.edu/pips/simazine.htm Environmental Fate section.


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## Guest (Sep 13, 2021)

I use .75 oz per 1k split app 30-45 days apart for poa in conjunction with specticle FLO


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## cldrunner (May 14, 2019)

@UltimateLawn

https://content.ces.ncsu.edu/princep-simazine-simazine

From the above link:
Residual Activity
Three to six months of broadleaf weed control can be expected, depending upon rate, soil type and environmental conditions.

I assume applied at 1.1 oz to 2.2oz. from the info at top of the linked page.

I have always thought exactly as @Bombers stated. Shorter life than others.


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## jasonbraswell (Aug 18, 2019)

My simazine label says 1 qt/A after Oct 1 for poa control and another 1qt in the spring.
Don't exceed 2 qts a year


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## cldrunner (May 14, 2019)

@jasonbraswell I think @UltimateLawn understands the label rates. He wants to know how long Simazine is effective in the soil. If .75 oz/1000 was used I suspect only 2-3 months according to the data in the NCSU article if one interpolates the numbers given. From some farming research it look like residue could stay in the soil for up to a year. I think once Simazine reaches half life in the soil it no longer is effective on weeds.


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## Amoo316 (Jul 8, 2021)

Maybe I'm wrong about this, but I was under the impression the biggest limiting factor on most pre-ms was soil mobility. As in rain pushes it out of the effective zone before the end of it's entire half life.

Kind of the same reasoning for doing split apps instead of 1 full app.

We're multiple feet above our average rainfall this year. If I wasn't growing baby bermudas this year in some spots and was pre-M I would have put down a summer app for that reason.


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## Movingshrub (Jun 12, 2017)

0.75 fluid ounces per 1k is the rate.


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## Amoo316 (Jul 8, 2021)

Per the label










also for annual rates


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## cldrunner (May 14, 2019)

@Amoo316 Some pre emergents are more soluable than others making them more mobile. Prodiamine stays in the soil longer even if you get higher rainfall. Prodiamine would stay in the soil longer that Simazine. I think indaziflam has even lower water soluability.

https://grdc.com.au/resources-and-publications/groundcover/ground-cover-issue-116-may-june-2015/water-solubility-key-to-effective-pre-emergents

Simazine is highly soluable which also makes it more prone to leach into shallow water tables or into ditches and streams. This is the main reason we may see Simazine taken away from the residential in the next few years.

I think this is why we see some pre emergents say water in a 1/4 inch while some other I have seen say 1-2 inches.


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## Amoo316 (Jul 8, 2021)

cldrunner said:


> @Amoo316 Some pre emergents are more soluable than others making them more mobile. Prodiamine stays in the soil longer even if you get higher rainfall. Prodiamine would stay in the soil longer that Simazine. I think indaziflam has even lower water soluability.
> 
> https://grdc.com.au/resources-and-publications/groundcover/ground-cover-issue-116-may-june-2015/water-solubility-key-to-effective-pre-emergents
> 
> ...


Yeah that was the overall point I was trying to make about soil mobility. I wish that table had more pre-Ms on it. I would assume Simazine is similar to Atrazine in regards to mobility.


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## cldrunner (May 14, 2019)

@Amoo316 Some of the SDS have the mobility number. I'm going to search around some scholarly articles to see of I can find some better research numbers.


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## Amoo316 (Jul 8, 2021)

cldrunner said:


> @Amoo316 Some of the SDS have the mobility number. I'm going to search around some scholarly articles to see of I can find some better research numbers.


Sounds good. I'm in the toughest stretch of my season right now and will be gone for 2 of the next 4 weeks so my "hobby" time is limited. I'd be interested in seeing Simazine, Prodiamine, Indaziflam and Oxadiazon specifically if you are taking requests :mrgreen: :lol:


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## jasonbraswell (Aug 18, 2019)

cldrunner said:


> @jasonbraswell I think @UltimateLawn understands the label rates. He wants to know how long Simazine is effective in the soil. If .75 oz/1000 was used I suspect only 2-3 months according to the data in the NCSU article if one interpolates the numbers given. From some farming research it look like residue could stay in the soil for up to a year. I think once Simazine reaches half life in the soil it no longer is effective on weeds.


Sorry I can't over analyze this. 
1 qt/A in October
Follow up with another Qt/A in early spring.
Don't use it in summer.


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## cldrunner (May 14, 2019)

jasonbraswell said:


> cldrunner said:
> 
> 
> > @jasonbraswell I think @UltimateLawn understands the label rates. He wants to know how long Simazine is effective in the soil. If .75 oz/1000 was used I suspect only 2-3 months according to the data in the NCSU article if one interpolates the numbers given. From some farming research it look like residue could stay in the soil for up to a year. I think once Simazine reaches half life in the soil it no longer is effective on weeds.
> ...


The OP @UltimateLawn has St. Augustine. Do you see any reason why he could not use 1.5 qt/ A for each application?


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## jasonbraswell (Aug 18, 2019)

cldrunner said:


> jasonbraswell said:
> 
> 
> > cldrunner said:
> ...


The label says you can put down up to 2 qts/A on St Aug.


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## UltimateLawn (Sep 25, 2020)

Lots of discussion here...thanks for the contributions. Correct...my question is not about the Simazine app level as much as it is around the decay of effectiveness over time. Prodiamine WDG and Specticle Flo have guidance here from the manufacturer/label. I can't see that Princep has done the same.

There are external resource links that have been shared and it seems reasonable that at lower rates we can expect about 3 months and at higher rates, 6 months. Maybe lower means 0.5-1 quart per acre and higher means 1.5-2 quarts per acre (?).

@Bombers , the prodiamine time/decay chart is from the prodiamine WDG label. The Specticle Flo time/decay charts are from the Bayer Specticle Flo Reference Guide at this link...

https://www.domyown.com/msds/Specticle_FLO_reference_guide.pdf

Given all of this and balanced with my complementary Prodiamine and Specticle Flo as well as helping my grass root out of dormancy, I'm doing this app plan. I think it should give me good coverage, multiple MOA's and consider decay up to the level of weed control without too much of a hit on the St Aug.

*Fall Round 1 (already applied)...*
Sunniland Prodiamine WG (65% Prodiamine) - 0.183 oz = 5 grams / 1,000 ft² = 3 Months of Pre-Emergent protection
Specticle Flo (7% Indaziflam) - 6 floz / acre = 0.138 floz / 1,000 ft² = 6 Months of Pre-Emergent protection
*Princep (41.9% Simazine) - 16 floz / acre* = 0.37 floz / 1,000 ft² = 3 Months of Pre-Emergent protection

*Fall Round 2...*
Quali-Pro Prodiamine WG (65% Prodiamine) - 0.183 oz = 5 grams / 1,000 ft² = 3 Months of Pre-Emergent Protection
*Princep (41.9% Simazine) - 16 floz / acre* = 0.37 floz / 1,000 ft² = 3 Months of Pre-Emergent Protection

*Spring Round 1...*
Quali-Pro Prodiamine WG (65% Prodiamine) - 0.183 oz = 5 grams / 1,000 ft² = 3 Months of Protection
Specticle Flo (7% Indaziflam) - 1 floz / acre = 0.023 floz / 1,000 ft² = 1 Month of Pre-Emergent Protection
*Princep (41.9% Simazine) - 16 floz / acre* = 0.37 floz / 1,000 ft² = 3 Months of Pre-Emergent Protection

*Spring Round 2...*
Quali-Pro Prodiamine WG (65% Prodiamine) - 0.09 oz = 2.5 grams / 1,000 ft² = 1.5 Months of Protection
*Princep (41.9% Simazine) - 8 floz / acre* = 0.185 floz / 1,000 ft² = 1.5 Months of Protection

Last year I applied based on annual max rates. While my lawn had very little winter or spring weeds, it was the slowest lawn to green-up compared to my neighbors (by far). I don't know for sure, but I think the Specticle Flo may have packed a pre-emergent wallop that had a higher impact on the St Aug Spring root development. This time I'm trying to have Specticle focused more on the winter weeds/poa since it's level has longer to decay with a slight boost in the early Spring to keep the crabgrass seed viability down.

Thoughts anyone?


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## Amoo316 (Jul 8, 2021)

Are you going to be out of all of your pre-M windows by the time August rolls around? Don't know your dates well enough for where you're at.

You might also consider starting Sulfentrazone at Spring 2 as a Pre-M for your nutsedge you've been battling.

[media]https://www.youtube.com/watch?v=20GHnEa8L0Q[/media]


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## UltimateLawn (Sep 25, 2020)

Amoo316 said:


> Are you going to be out of all of your pre-M windows by the time August rolls around? Don't know your dates well enough for where you're at.
> 
> You might also consider starting Sulfentrazone at Spring 2 as a Pre-M for your nutsedge you've been battling.


I don't believe so. My rates shouldn't get to the max and I typically don't do any Summer applications. Two in the Fall, two in the Spring.

I've found on my StAug that Dismiss/Sulfentrazone is too destructive unless applied under the grass blades at the soil level just above the nutlet. It definitely kills the nutsedge swiftly, but I'm chasing them all over the lawn spot spraying for each.

I am planning on using Halosulfuron/SedgeHammer once the nutsedge starts to emerge from dormancy. It seems to treat my St Aug much better, but it kills very slowly (30+ days). Hopefully it will slow down the nutsedge before it becomes an eye sore throughout the next season.

I have also had good results with Sulfusulfuron/Certainty in terms of nutsedge control with a faster take-down than Halosulfuron. It seems to be middle of the road compared to the other two. I don't want to risk the early part of the season with a broadcast spray that I regret. As long as I can wait for the knock-down, Halosulfuron seems to be the best option.

Also...I've heard that there really is not a good pre-emergent for Nutsedge that is very effective as compared to other broadleaf weeds. Best done as post...or at least that's what I've seen.


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## Amoo316 (Jul 8, 2021)

I'm guessing you don't end up with late emerging summer weeds then? That was more what I was getting at by only offering protection for the first little bit of summer with lower spring rates.

RE Nutsedge Pre-M: The video I posted is definitely worth your time in regards to pre-M control for Nutsedge and different programs and options. He lays out a myriad of different options that are available, some of which I'm assuming would be fine on your St Aug.


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