Knowledgebase

Turf Grass: Disease Identification & Treatment #919125

Asked October 02, 2025, 8:35 PM EDT

Dear Master Gardener Team, I was wondering if you could help me idenfity the disease/fungus that has developed in a very small part of my lawn. I recently overseeded several sections of my lawn with a 70/30 blend of Kentucky Blue Grass and Perennial Ryegrass. Prior to overseeding I aerated the lawn then laid down the seed and top dressed with 1/4-1/2" of peat moss. For the first 14 days I was watering 4 times a day for roughly 6 minutes per time. I have now ratched back to watering for 8-10 minutes twice a day. I noticed that some white powdery substance started growing near the driverway directly on the soil. I have attached pictures of the areas in question. Can you help me identify the disease/fungus and guide me in how to resolve the issue? My fear is that this will spread to throughout my lawn and I don't want to let it get out of control where to where I will need to be treating my entire lawn with some sort of fungicide for the rest of time. Please feel free to call if you have any questions. Thanks for your guidance.

Hennepin County Minnesota

Expert Response

The depth of water penetration is what should be measured rather than the amount of time watering is done. Too much water may be contributing to the mildew. Your grass has germinated, so check the soil to see that it is moist but not sopping. Your driveway edges may be accumulating more water than is needed. See these web pages. 
https://www.extension.purdue.edu/extmedia/bp/bp-111-w.pdf
https://www.canr.msu.edu/ipm/diseases/powdery-mildew?language_id=
https://extension.umn.edu/lawn-care/seeding-and-sodding-home-lawns

Linda,
Happy Friday! First, thank you for the prompt and informative reply. I have taken note of your guidance and I have read through the links you attached. I really appriciate your sharing your knowledge with me. Thank you.
I do have a couple follow up quesitons:
#1. Based on the pictures I provided, what do you think it is that is growing on the solid?
#2. I read the link regarding Powdery Mildew. This appears to be mostly on the leaves. Does it appear on the soil?
#3. What should I do to treat it/contain it as to not have it spread to other parts of the lawn?
Thank you again for your prompt reply and sharing your knowledge with me.

The Question Asker Replied October 03, 2025, 11:58 AM EDT
Linda, 

Happy Friday! First, thank you for the prompt and informative reply.  I have taken note of your guidance and I have read through the links you attached.  I really appriciate your sharing your knowledge with me.  Thank you.

I do have a couple follow up quesitons:

#1.  Based on the pictures I provided, what do you think it is that is growing on the solid?

#2.  I read the link regarding Powdery Mildew.  This appears to be mostly on the leaves.  Does it appear on the soil?

#3.  What should I do to treat it/contain it as to not have it spread to other parts of the lawn?

Thank you again for your prompt reply and sharing your knowledge with me.




From: ask=<personal data hidden> on behalf of Ask Extension
Sent: Thursday, October 2, 2025 8:09 PM
To: Ed Young
Subject: Re: Turf Grass: Disease Identification & Treatment (#0189041)
 
The Question Asker Replied October 03, 2025, 12:10 PM EDT
Send a sample of the soil and the grass to the Plant Disease Clinic   https://pdc.umn.edu/
Call them first and see if they want two separate samples or not. 

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