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PGR for St. Augustine, Houston TX

3K views 71 replies 8 participants last post by  CenlaLowell  
#1 ·
I've tried Syngenta Primo Maxx at .15 oz/gal water with no effect. I've increased to .2 oz with no effect. I've reapplied at 125 GDD with no effect. Any thoughts? Another PGR I should try?
 
#2 ·
What do you mean that you've seen no effect? Growth doesn't seem to slow down? Not seeing darker grass? What effect are you expecting?

Are you spraying 1 gal./1k sq. ft.?

My CitraBlue didn't show a response to T-Nex until after the second application. I sprayed at 0.15 oz./M. After the second application growth almost shut down entirely and the stolons started to grow tight with tiny leaves.
Image
 
#15 ·
My CitraBlue didn't show a response to T-Nex until after the second application. I sprayed at 0.15 oz./M. After the second application growth almost shut down entirely and the stolons started to grow tight with tiny leaves.
Thank you for info as I also have Citra Blue and plan to dabble a bit with T-Nex as well.
 
#10 ·
Do you know what St. Augustine cultivar you have? As you see on the label, different cultivars within the same species require different rates of T-Nex. T-Nex isn’t commonly used on St. Augustine so you won’t find much information about it online. Maybe your cultivar needs a higher rate.

Bump up your mixture to 0.30 fl. oz./gal. T-Nex for the next application and see what happens. If no effect, go to 0.40 fl. oz./gal. T-Nex after that.

Can you take a picture of the end of some of your stolons and share them here?
 
#12 ·
From the Primo MAXX label:
Mowing
Generally, Primo MAXX provides more suppression when turfgrasses are maintained at lower mowing heights than
higher mowing heights. Application rates have been selected for typical mowing heights. The application rate may
need to be adjusted depending on actual mowing conditions.
Looks like you're maintaining your SA pretty tall. Assuming that you're spraying properly, I think you just need to increase the rate of T-Nex in your mixture until you start seeing the suppression you want.
 
#13 ·
Start off with a low dose of PGR until you observe how your grass responds. My SA is extremely sensitive to PGR.
 
#17 ·
What height are you maintaining your Citra Blue at sir?

I have varied mine from about 2" to 4" and settled on ~3.5". This cultivar is definitely easier to maintain lower than the usual St. Aug suspects (which around here are floratam, bitter blue to some degree and, here and there, some palmetto).

And out of curiosity----

How does the Citra Blue handle winter in ATL?
 
#25 ·
If you are using the 230 GDD reapplication interval, you should be calculating using the 10°C base. Most of us will reapply around 225 to 250. The 50°F will give you significantly higher numbers which could cause you to stack applications and overapply.
 
#31 ·
I use Lawn Track App to track all my applications but it no longer tracks GDD so I set up a threshold on GreencastOnline. GreencastOnline will also send you an email notice when you get to 90% and then again at 100% of your reapplication interval. Set it up using the 10°C base and at a minimum you can use it to double check your numbers from any other apps.
 
#38 ·
Can you walk us through exactly what you’re doing? How many sq. ft. is your lawn? How many gallons of water are you mixing? How much T-Nex total (not per gallon) are you putting in the tank? Are you mixing anything else in? Are you running your sprinklers after spraying?
 
#39 ·
The lawn is 2,800 sq. ft. I use 2 gallons of water for 2,000 sq. ft and one gallon for the 800 sq ft. When I made the two gallon mix on 7/17, I used .55 oz of T Nex and .275 oz for the one gallon mix. I did add surfactant to both and didn't irrigate for two days after application. I use a T jet fan nozzle on my Flowzone Cyclone 3 sprayer.
 
#45 ·
Maybe you two aren't seeing much of a response due to your HOC? I maintained my CitraBlue at 2". I'm sure that the regulated SA that @Redtwin posted a picture of isn't mowed >3".

From the Quali-Pro T-Nex label:
For greater suppression with Quali-Pro® T-Nex®, maintain turfgrass at lower mowing heights. Note that the rates given in the APPLICATION RATE TABLE are for turf at typical mowing heights; therefore, the application rates should be adjusted based on the grass height at application. The lower the height of cut of the particular turfgrass species, the less material is required to provide the desired turf growth regulator effect.
Years ago @Zoysiaguy shared that he was spraying T-Nex at 1.0 fl. oz./gal. on his Palmetto St. Augustine maintained at 2" and he was seeing regulation: https://www.thelawnforum.com/posts/118702/. That's a significantly higher rate than you two are spraying.

@813king made a post showing his St. Augustine lawn mowed under 0.5" and regulated with PGR, but he never shared application rates: https://www.thelawnforum.com/threads/under-0-50-reel-mowed-st-augustine.32614/

@TampaBayFL you should consider dropping your HOC. Dr. Kenworthy recommends a lower HOC for CitraBlue and it looks so good at 2". My CitraBlue also only got 3.5 hours of sun per day, I imagine yours gets more. I don't think sun exposure would make a difference, but maybe?
 
#47 ·
@TampaBayFL you should consider dropping your HOC. Dr. Kenworthy recommends a lower HOC for CitraBlue and it looks so good at 2". My CitraBlue also only got 3.5 hours of sun per day, I imagine yours gets more. I don't think sun exposure would make a difference, but maybe?
I have mowed it as low as 1.5" and all the way to 4"! It did not look good much lower than ~2.5" in my yard. The 3-3.5" range seems to be the best overall height for my yard for whatever reason.

I have areas of the CB that probably get sun 12+ hrs a day and others which get alot less and it seems happy with both conditions. This variety is definitely much much better than something like Floratam in shade.
 
#46 ·
FWIW, the area I showed photos of gets 100% full sun all day and zero irrigation other than rain. It's also under severe weed pressure from torpedograss, bermuda, and spurge. I only spray what's left in my tank and the max rate would be .38oz/1000sf. If I use a tank from the frontyard, it would only be .25oz/1000sf. It is mowed at 1.25" if I mow it but usually my neighbor hits it with his zeroturn and scalps the crap out of it. It's a neglected area for sure, which made the appearance of the SA even more amazing to me.
 
#49 ·
Why try to PGR St. Augustine in the first place? Can someone explain that. It's high HOC makes it shade tolerant, drought tolerant, aggressively spread and healthy but likely poorly responsive to PGR. Its drawbacks are fungus, thatch and IMO appearance. I doubt making it more compact would improve that. I'd just leave it alone. But maybe I'm missing something? Anyone who's regulating their St. Augustine want to post before and after photos. I've just never really considered that this could be a thing.
 
#55 ·
That looks like regulated CitraBlue! Your last application was on July 25, right? Are you mowing less now?
Yes, I applied at the 0.15 rate/1k on 7/8/25 and 7/25/25. I believe I am due for the next app now.

The growth rate has definitely slowed down now for sure.
What didn't look good about the CitraBlue when you mowed under 1.5"? Scalping?
Yeah....it just looks stressed and much much less blue/green. Even at ~2.5" now I can see those same visual cues. My mower also has a hard time cutting super cleanly at the lower HOCs as the Citra Blue has gotten quite thick with many blades crunched together vertically (they are standing up like pickets on a fence). I suspect my mower simply doesnt have the blade speed (and motor hp) to really give a good cut in this situation.
 
#62 ·
I suspect my mower simply doesnt have the blade speed (and motor hp) to really give a good cut in this situation.
To follow up with this----

I mowed a small section at a lower height with a push reel mower and it did look pretty bad @$$:p

But, the effort level was so high that it is not practical for even my small lawn. I had to go over each area quite a number of times to get all the stragglers and have an even cut and the reel continuously stalls as the wheels slip on the grass due to the cutting effort required.