# Do you guys rotate pre emergents?



## Lawn Smith (Jun 8, 2020)

My last 3 treatments of pre emergent have all been with Prodiamine and didn't know how important it is to rotate them? I rotate my fungicides with 3 different MOA's but you don't hear much about rotating herbicides.


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## Mightyquinn (Jan 31, 2017)

I never have used anything but Prodiamine and never had an issue but I'm not religious about putting it out either. Having a healthy thick lawn will take care of 90-95% of your weed problems if not more. Pre emergents are just insurance.


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## Sonoran Desert Lawn (Aug 22, 2020)

I had a weed factory 2 years ago. At least 90% crabgrass in my bermuda. Last year I calculated the max volume output allotted between prodimiane and Spectracide Weed Stop (aka Dithiopyr) then divided the amount into equal monthly numbers. I switched the two every other month and had a 99.9% weed free back and front yard. It worked wonderful so that's what I am doing again in 2022


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## CenlaLowell (Apr 21, 2017)

Yes I have but next year I'm only running one pre emergent a year. After a few years of doing that you will have little to no weeds in your lawn.


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## Monocot Master (Feb 28, 2021)

I have been making three granular apps per year of Dithiopyr. Split spring apps + one fall. The annual max of dithiopyr is quite high, but that is not why I use it. I find that it controls lespedeza well is why I like it. I may start using prodiamine in the fall since I am doing some liquid applications now, so will get more even coverage and it is cheap.


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## FATC1TY (Jul 12, 2017)

Nah. I use the same old tired Specticle every year. No reason to change if it works.


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## paulwrunge (Dec 13, 2021)

I was using granular Pendimethalin for years and never could control Harry Bittercress. Switching helped control it. Now that I can spray I will continue to rotate and do split applications.


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## Keepin It Reel (Feb 20, 2019)

I started doing a 3 way tank mix consisting of 2 pre-ems, and 1 post em this year and so far the results have been great. I used Prodiamine exclusively but I found the POA control was pretty much non-existent and last year I had more POA than i ever have before.


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## Guest (Jan 3, 2022)

FATC1TY said:


> Nah. I use the same old tired Specticle every year. No reason to change if it works.


+1


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## Jeep4life (Jun 19, 2019)

FATC1TY said:


> Nah. I use the same old tired Specticle every year. No reason to change if it works.


Are you taking the yearly max and dividing it by 2 to get your spring and fall apps?


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## cglarsen (Dec 28, 2018)

Keepin It Reel said:


> I started doing a 3 way tank mix consisting of 2 pre-ems, and 1 post em this year and so far the results have been great. I used Prodiamine exclusively but I found the POA control was pretty much non-existent and last year I had more POA than i ever have before.


My yard is full of POA on prodiamine too. What did you add to control it?


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## Bombers (Jul 14, 2020)

cglarsen said:


> Keepin It Reel said:
> 
> 
> > I started doing a 3 way tank mix consisting of 2 pre-ems, and 1 post em this year and so far the results have been great. I used Prodiamine exclusively but I found the POA control was pretty much non-existent and last year I had more POA than i ever have before.
> ...


Simazine is cheap to add in the fall application if you're stocked up on Prodiamine. Their efficacy is shorter than most pre-E so I would time it close to germination temp to make it last until early spring. Or go all out and get Specticle Flo/Esplanade and be worry-free about weeds.


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## Jagermeister (May 18, 2021)

cglarsen said:


> Keepin It Reel said:
> 
> 
> > I started doing a 3 way tank mix consisting of 2 pre-ems, and 1 post em this year and so far the results have been great. I used Prodiamine exclusively but I found the POA control was pretty much non-existent and last year I had more POA than i ever have before.
> ...


I had good results with prodiamine, indaziflam, simazine mix and then ran two apps of Negate as I had early germination of poa back in September. Lawn is now weed free! many other homes with low cut lawns or thin spots have poa all over them!


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## FATC1TY (Jul 12, 2017)

Jeep4life said:


> FATC1TY said:
> 
> 
> > Nah. I use the same old tired Specticle every year. No reason to change if it works.
> ...


I did the first year or two, but I recently cut down on my application rates, as I want to use as little as I can, and not have any weeds. I rarely ever find a weed, maybe near a sidewalk crack or driveway edge.

I'd have to look back at some notes and figure it out, but yeah, it's a pretty safe bet to assume the yearly max, split and go with it. I think I go with 7oz/acre rate if not mistaken.


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## Lawn Whisperer (Feb 15, 2021)

Lawn Smith said:


> My last 3 treatments of pre emergent have all been with Prodiamine and didn't know how important it is to rotate them? I rotate my fungicides with 3 different MOA's but you don't hear much about rotating herbicides.


Herbicide resistance is real, it's just a matter of time and combination of weed and herbicide. It's hard to change something that you know works.

Here is an  article from TAMU  and NVS8jTiWFo8][/MEDIA] a video from TGF.

I haven't had personal experience with encountering herbicide resistance weeds with multiple yearly apps, but others might be able to share their experience.


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## zeroibis (Sep 28, 2020)

Monocot Master said:


> I have been making three granular apps per year of Dithiopyr. Split spring apps + one fall. The annual max of dithiopyr is quite high, but that is not why I use it. I find that it controls lespedeza well is why I like it. I may start using prodiamine in the fall since I am doing some liquid applications now, so will get more even coverage and it is cheap.


Your observation is correct and I have been thinking about using it for my summer application for this reason due to getting a lot of lespedeza this past year.

For reference UGA rates dithiopyr as having Excellent performance against lespedeza and prodiamine as poor and pendimethalin none.

However, the real summer trade off is that it only rates dithiopyr for crabgrass as Good-Excellent vs Excellent for prodiamine and pendimethalin. It might not be a huge difference but it exists.

Other differences include:
dithiopyr vs prodiamine 
annual bluegrass G vs E (not an issue in summer really)
goosegrass Fair vs G
corn speedwell G vs none
spurges G vs none

Also just wanted to add a warning about indaziflam as it was referenced earlier in the thread. From UGA: "Do not apply to desirable cool-season grasses, golf greens, or within 15 ft of golf greens. Indaziflam may affect sensitive grasses down slope from treated areas, do not use on slopes uphill and adjacent to bentgrass or bermudagrass golf greens"


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