# pre-emergent applications and timing



## Flanders (Jul 5, 2019)

I need some help with pre-emergents. I live in northern Alabama and have a Bermuda lawn.

I am VERY unclear about EXACTLY when to put down pre-emergent. I've seen anywhere from January to late March for the first application. I've seen when soil temperatures reach 52 degrees, and I've seen when the frosts are done. If it's based on soil temperature, what about when it dips back down and then raises back up to 52 again? Do I need to reapply again?

Then a fall application anywhere from August to October. I have no idea how to know when to apply for optimum effectiveness.

I have Prodiamine (Barricade) that I spray and was considering picking up some Dithiopyr (Dimension). So, is it recommended to do just the 2 pre-emergent applications per year, or more? If using 2 different pre-emergents, should I spray one soon after the other, or wait weeks or months between the two? And timing - WHEN do I apply the pre-emergents?


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## calebbo (Jul 30, 2019)

If you start at the beginning of the year it's cold.

Warms up in February/March to 55 degrees.

You want to lay down Prodiamine before it hits 55 degrees. So hit it at 52 degrees. I use the 5 day average to find the right time.

I do 0.2 oz of Prodiame per 1,000 sqft. I calibrated my sprayer to spray 1 gallon of water per 1,000 sqft. So I put 0.4 oz in my 2 gallon sprayer and spray 2,000sqft.

Refill and preventive kill my yard.

Make sense so far?

That will give you over 2 months of protection.

Next temperature range is 70 degrees. (we started at the beginning of the year so it's warming up)

So I would hit it around the 67 degree mark. I use the 5 day average and when it hits 67 I spray another 0.2 oz per 1,000 sqft. That's 2 more months.

Finally, summer comes. It's hot as balls. Weeds are kind of done germinating. So you use post emergent to slay bodies now. Whatever broke through your defense. Kill it.

Fall comes. Kind of where we are now. Summer is ending and fall is approaching. The weather is cooling down. Soil temp begins to drop (not for me, it's still hot in OKC and Texas)

BUT

When the soil gets to 55 degrees again you want to put down prodiamine again. I'll hit it when the 5 day average is 58 degrees or so (weather is cooling down so now you need to lay down the P when it's slightly above 55 degrees)

But DONT use 0.2 oz per 1,000 sqft

You need the Prodiamine to last you through winter until the Temps raise back up to 55 degrees again in the Spring.

The max allowed use of prodiamine is 0.83oz per 1000sqft per year.

You used 0.2 oz for application 1

You used 0.2 oz for application 2

That leaves you with 0.43 oz per 1,000 sqft for your winter to spring application at 58 degrees soil Temps.

IDC about max rates so I probably would do 0.5 Oz to make it easier on myself lol

It's my first year using prodiamine. Just bought a house in May. But that's what I've learned so far.

I haven't used dimension but I would probably wait a week if you were to use it.

I thought they had the same mode of action (moa) so idk why I would spend the money.

I use celsius and Certainty as post emergent herbicides. Blanket spray Celsius. Wait 4 weeks. Whatever doesn't die use certainty. Reapply Celsius as well at the same time. Wait 4 weeks. Whatever is left standing buy some glyphosate or whatever and murk bodies.

I use 3.2 grams per 1000 sqft of Celsius 
2 gallon sprayer so I just round up to 7 grams. My scale doesn't have that level of precision and accuracy.

I use the 1.25 lb per acre of certainty.
(5 small scoops of certainty per 1000 sqft)
Scoop comes with the bottle.

Don't sweat the dates for applications. That stuff doesn't matter. It's all about soil Temps. If you havent out down prodiamine yet just do it now and follow the above stuff. People will say it's too late since weed seeds have already germinated but in my mind I just want to prevent any late stragglers. Plus a bottle of Prodiamine is supposed to last like 19 years or something. I've got product to waste haha

Hope that helps


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## calebbo (Jul 30, 2019)

Also

Water in your prodiamine. I'd wait until the next day after I applied it then water it. Some people say a 1/4 in of water is necessary.

I just waited for my 1in watering day. I'm in the midst of summer and we don't get rain. I water on Sundays. So I laid my prodiamine down Saturday. Watered Sunday morning.

I cut my grass on Mondays and Thursdays.

Mow 2 days before you lay down prodiamine. Lay the P down. Wait 24 hours. Water it in. Continue on with life. Don't aerate or break the soil surface or you'll screw up your prodiamine barrier.

With Celsius and Certainty don't mow two days before or after you apply the product. I don't think you have to water them in. Just let them dry on your grass. Make sure it doesn't rain within 4 hours of applying. So don't run sprinklers after you lay down the C&C Hammer.


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## bigmks (May 22, 2018)

:thumbup: Very good strategy! Well written as well.


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## lawn789 (Jun 16, 2019)

Thanks @calebbo


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## Flanders (Jul 5, 2019)

@calebbo thank you for the detailed response, that's great. I'll go by those guidelines and see how it goes.

I do still have a question - so let's say I get to the 5 day average and spray. What about if the temps drop down again for a few weeks? Do I need to spray again when the soil temp goes back up, or is that first spray going to hold up even though the soil temps dropped into the mid 40s, for example?

Also, I've seen where people said they use Barricade AND Dimension. Is that just unnecessary? I haven't done well with preemergents in the past (probably putting it down at the wrong times) so I was thinking of doubling up. I guess if I just use the Prodiamine correctly it should be okay by itself though?

Also, since mentioned celsius ... I learned the hard way this year that 2, 4-d while very effective can be bad for Bermuda grass when sprayed in high temperatures. Oops. Fortunately, those yellow spots are greening back up now, and without the weeds, so it looks like it will be fine. But, since I had this happen, I've read that Celsius (I believe it was Celsius) can be applied at ANY temperature and it won't hurt or yellow Bermuda grass. Would you agree with that?


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## calebbo (Jul 30, 2019)

Flanders said:


> @calebbo thank you for the detailed response, that's great. I'll go by those guidelines and see how it goes.
> 
> I do still have a question - so let's say I get to the 5 day average and spray. What about if the temps drop down again for a few weeks? Do I need to spray again when the soil temp goes back up, or is that first spray going to hold up even though the soil temps dropped into the mid 40s, for example?
> 
> ...


Prodiamine works by soaking into the soil and creating a barrier.

If your 5 day average is in that window you're applying the product to the grass. Then watering it in the next day. This allows the prodiamine to soak into the soil thus creating your barrier.

If your fall application of P is supposed to last through winter until Spring when the Temps raise back up to 55 degrees I don't see how a change in temp will affect your barrier once it's already applied (since it was applied prior to freezing temperatures)

Also yes, I agree. I just C&C'd my yard recently and it's been hitting 104+ here. So far so good.

Just calibrate your sprayer. Fill it up with 1 gallon of water. Mark off two or three 1,000 sqft areas. Buy some blue dye for spraying at home depot or something and calibrate.

You can hinder Bermuda growth by overapplying C&C.


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## adgattoni (Oct 3, 2017)

The goal of the spring pre-emergent application is primarily to prevent summer grassy weeds like crabgrass. The temperature target is based on the ideal temperature for crabgrass germination. That is around 55 degrees, thus you want to get your barrier down prior to that (52 as mentioned here).

Once that barrier is established, it will provide residual control according to the rate you use (I typically do two applications a year at the 6-month rate). If you apply when temps average 52 and it drops to 40, you do not need to reapply since the barrier has already been established. It's only important to get the barrier established prior to 55 degrees since crabgrass will begin to germinate around that temperature. I do my spring app in late February to avoid the rigamarole of monitoring temperatures.

Dithiopyr (Dimension) is sometimes used instead of prodiamine (Barricade) since it provides post-emergent control of young crabgrass. The theory being if you miss the window you can use dithiopyr to kill the crabgrass that has germinated and prevent more from popping up. My perspective: just buy a jug of prodiamine and if you miss the window, go out with prodiamine and quinclorac. Cheaper than keeping both prodiamine and dithiopyr on hand all the time.


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## Bmossin (May 31, 2018)

calebbo said:


> Finally, summer comes. It's hot as balls. Weeds are kind of done germinating. So you use post emergent to slay bodies now. Whatever broke through your defense. Kill it.


Made my day


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## Flanders (Jul 5, 2019)

@adgattoni thank you for that explanation

@calebbo thank you for all of the information

I felt a bit lost when it came to preemergents when I posted this. Now, I don't have any questions. I really appreciate the time you guys took to help.


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## corneliani (Apr 2, 2019)

Here's a writeup by the LCN that falls right in line with what the guys above have been telling you, for confirmation/reiteration sake: 
https://thelawncarenut.com/blogs/news/how-to-apply-a-split-application-with-prodiamine-wdg-pre-emergent-herbicide#


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