How to treat infected buffalo grass?

[jonniemartin]

I recently did a backyard renovation which included rolling out new Sir Walter Buffalo turf (November 2023). The area sits on a clay base, so we decided to dig down 150mm and backfill with soil, to give the grass a better foundation. The lawn was initially doing really well and growing thickly.

However, recently I think I'm dealing with a pretty significant fungal infection. On reflection, this is likely due to me overwatering the area. At first, areas of the lawn began to thin out, with olive coloured spots appearing on the leaves. These worsened and then started to form brown patches all over the lawn.

After reading some advice on a similar issue, I have aerated the entire lawn and top dressed the brown patches with washed sand, as well as holding off on watering until the lawn is completely dry. I have also applied a round of Sulphate of Potash to the whole lawn (link) to try and speed along the recovery. This was applied about one week ago now.

Since applying the fertiliser, topdressing and aerating - the infection has not gotten significantly worse, but it hasn't really improved either. My main questions:

1. At what point should I look at applying a fungicide, if the mentioned treatment doesn't work?

2. Which fungicide should I apply and is there any risk in applying one when the lawn is so young?

Please see below pictures:

18th November - Clay base Dugout

18th November - Clay base dug out

18th November - Backfilled with Soil

18th November - Turf Layed

23rd December - Lawn Growing Well

8th January - Brown Patches and Fungus Pictures

Today (9th January) - Top-dressed and Aerated.

[Jewelleryrescue]

Hi @jonniemartin 

Looks  like Grey leaf spot a  pathogen that occurs  when buffalo grass under plant stress and prolonged leaf wetness humid weather too.

Keep lawn short to help it dry out.

Sesol the  lawn area may help and not hurt  lawn

 Yates  makes several   fungus sprays  that  can apply to your grass as a last resort

Yates 200ml Liquid Copper Fungicide 

I/N: 3010236

$21.54

https://www.bunnings.com.au/yates-200ml-liquid-copper-fungicide_p3010236

[jonniemartin]

Thanks @Jewelleryrescue. Is there any issue in applying Seasol to the lawn area, approx ~2 weeks after appyling a granular fertiliser? Richgro 2.5kg Granular Sulphate Of Potash - Bunnings Australia.

If I dont see noticeable improvement within a couple weeks, would you then say its time to apply the fungicide as last resort?

[Jewelleryrescue]

Hi @jonniemartin 

Seasol it like a tonic to plants not really a  fertiliser (Food)   so  you wont be over feeding them.

Sort of like us  taking a multi vitamin 

[EricL]

Hi @jonniemartin 

Welcome to the Bunnings Workshop community. It's wonderful to have you join us, and thanks for sharing your question about your lawn.

It's good that you've carried out first aid and support for your lawn which is aeration and fertilizer. I highly suspect that water is still getting trapped underneath and is soaking the roots of your lawn. 

What did you use to aerate your soil? If you used the Saxon Lawn Aerator Sandals, I suggest taking it to the next level and using Saxon Fibreglass Long Handle Garden Fork. Go as deep ask you can and ever so slightly rock the fork to open up the soil.

This will provide more air circulation in the soil and hopefully accelerate evaporation.

Let me call on our experienced members @Noelle and @mich1972 for their recommendations. 

If you need further assistance, please let us know 

Eric

[mich1972]

Good evening @jonniemartin May I ask if there was coarse sand in the soil that you used ? Coarse sand will help with drainage. Also are you watering at night ? As that doesn’t help and increases the chances of fungal problems. I’m going to tag @Noelle for her expert advice. 😊

[jonniemartin]

Hey @EricL and @mich1972, thanks so much for the replies!

@EricL - For the aeration, I used a garden fork very similar to the one you linked. Since doing the aeration, the lawn is drying up much quicker when it rains, which is a good sign! 

@mich1972 - Previously I was watering in the afternoons, but have cut right back on watering since the symptoms started showing. I’m only watering once a week in the mornings now (if there’s no rain predicted). The soil I used is here: https://www.bcsands.com.au/landscaping/soil_garden_mixes/turf_gro_premium_top_dressing_turf_underlay.... I don’t think there was sand in the blend, but as the lawn continues to mature I’m planning on top dressing with sand to help out with drainage. 

Should I see if the brown patches and thinned out areas recover on their own now? And maybe look at a fungicide in ~2 weeks if no improvement?

Thank you! 

[mich1972]

Aeration with a garden fork is good and will definitely help !!!! Sounds like it’s starting to recover. It wouldn’t hurt to spray the fungicide in a couple of weeks if no improvement. Stay in touch and let us know how it goes. Please make sure to wear the appropriate protective gear if you are spraying any garden chemicals 🪴😊

[Noelle]

Hi @jonniemartin 

I agree with everything @EricL  and @mich1972  have advised regarding aeration and application of an appropriate lawn fungicide - Bunnings has a range of lawn-specific fungicides available.

Looking at your prep, in my opinion part of the problem is that you have dug down into the clay layer and created a lovely shallow "wading pool" that you have back-filled with quality soil. Water and rain will saturate the area of least resistance - the good soil lawn area - and drain into that area off the surrounding clay.  This makes aeration deeper than the topsoil layer imperative, to encourage moisture to soak down deeper into the clay layer.

Once you have solved the drainage issue and controlled the existing fungal outbreak, your lawn should flourish. However, you will need to remain vigilant and proactive in times of heavy rainfall and over summer when you irrigate. Water in the early morning whenever possible to allow the grass itself to dry off before evening.

[MitchellMc]

Hi @jonniemartin,

It's been a while since your last image was taken (9th Jan). Can you please update us on the condition of the lawn now?

You might need to do some exploratory work after the rain. Wait a couple of days and dig down to check if the soil 15cm under the surface is still saturated. If it is, this might be a case of needing to install drainage under the lawn to remove the excess water. If you don't get the drainage sorted, managing the lawn will be exceptionally hard, as it will always be either too wet or too dry.

Mitchell