It’s called Brown Patch disease when it infects cool-season lawns, and it’s called Large Patch disease in warm-season lawns but both diseases are caused by the pathogen Rhizoctonia Solani.
Here is a video I made this weekend showing its effects on St Augustine and Zoysia:
The times it shows up are during seasonal transitions. In south Florida, it’s coming out of winter into spring, or like now, fall into winter.
Here in my St Augustine and Zoysia, we were in the 80s with mild humidity and in the last 2 weeks have fallen into the upper 60s, no wind and no humidity.
Rhizoctonia thrives when outside temps are in the low-70s consistently overnight - night time is also when dew forms on the ground keeping things wet.
How many of you remember when we talked earlier this year about the disease triangle?
Our Treatment strategy utilizes products found at any local big box store. I am using a twist on my “bullet-proof” strategy which is meant for prevention but also works for curative applications.
The reason I call it “bullet-proof” is because we are using 2 different classes/groups of fungicides in our attack.
Think of these “classes” or “groups” as “modes of action.”
Scott’s DiseaseEx has active ingredient azoxystrobin which is a Strobilurin (Group 11) fungicide. These inhibit cellular energy production causing failure of the target fungi.
Bio-Advanced Fungicide has active ingredient propiconazole, a DMI (DeMethylation Inhibitor - Group 3) fungicide and works by blocking cell membrane production in certain fungi. Without this function, the fungi fails.
When you attack a fungus with 2 different modes of action or “from 2 different angles” you have a much better chance of stopping it. This can also help reduce resistance in the future.
You guys know that I oftentimes try to make recommendations of products that you can get locally at stores like HD or Lowes. I do that because in many cases these are cheaper and easier to apply. Plus, if you have a real problem, going to the store today is still faster than Amazon Prime shipping in most of the country.
That said, one of the “DIY” products I recommend, Scotts DiseaseEx, is also EXACTLY the same as the “professional” product.
Last year I wrote a VERY detailed guide on Fungicides and at that time, I offered some professional product options that some of you may want to consider - especially when it comes to the Group 3 fungicide options that can be applied via backpack sprayer.
Check out that post here.
Note - with all diseases, but especially with Rhizoctonia - prevention is the best medicine. It’s best to apply fungicides prior to the disease manifesting.
I should have applied back in October, but I didn’t because I have not had a brown patch problem here before. This Brown Patch - Large Patch In St Augustine, Zoysia, Tall Fescue video demonstrates me performing a corrective action instead of preventative.
The first thing I recommend you do after you apply your fungicide is taking pictures. Note how large the spots are and where they are.
Then take a picture a week later and compare… has the disease spread or have the spots gotten bigger?
If so, consider another application of the Group 3 propiconazole. Keep taking pics - if it’s still spreading a week after that, you can apply the Group 11 Scotts DiseaseEx again.
For me, it all stopped after the applications you see me doing in the video. We are also getting cooler temps which stops the disease naturally (but remember it stays in the soil over winter).
Either way, it’s going to take a few weeks for the damaged sections of the lawn to recover.
For one, growth is slow right now due to the cold and secondly, shorter days mean less sunlight which also slows growth.
Mowing will help to take away dead stuff and I’m also going to hose the area down with Air8, RGS, and D-Thatch this weekend. I plan to do a SUPER HEAVY soaking just because I have not sprayed hard in a while and I’m due.
In all seriousness, the humic acid in ALL of the N-Ext products is great for keeping soil life active which in turn supports more roots growth and can significantly speed up repair time.
That’s one more reminder too - often times people ask me, “Allyn can you show us the Ortho Dial-n-Spray John Perry mod again?”
Watch this "Weed Wack, Front To Back + Lawn Spraying Tests" video right here and it works great!
Also, don’t forget, we have GIFT CARDS still available if you are interested… plenty of time to get them to your house before Christmas!
I’ll see you in the lawn!