How To Prevent & Treat Brown Patch in Lawns

How To Prevent & Treat Brown Patch in Lawns

You survived another long winter. You jumped into your early spring lawn care plan and began the much anticipated hard work of clean-up, applied your first application of crabgrass control and prevention, fertilizer, and are starting to see the lawn quickly green up and grow like crazy. 

But soon both the outside temperature and humidity levels begin to rise and invites lawn diseases and funguses like brown patch.

Don’t ruin your hard spring lawn work and visions for summer and fall domination by allowing brown patch to ruin your plans. Follow this guide to help prevent and treat brown patch in your cool-season lawn.

What is Brown Patch

Brown patch is a very common cool-season turf disease caused by the Rhizoctonia species fungus. The cool-season grass type most affected by brown patch fungus is Tall Fescue.

  1. Preventative Rate
  2. Curative Rate

Types of Lawn Fungicides

  1. Systemic Fungicides
    Fungicides that are taken up and absorbed by the plant. Foliar applications which are absorbed by the grass blade – or drenching which is applying fungicide and watering it in to be absorbed by the plant roots.
  2. Contact Fungicides
    Fungicides that are not absorbed by the plant. These types of fungicides stay on the grass blade to protect the plant.

How to Prevent Brown Patch

The best mode of action against brown patch in cool-season lawns is of course prevention. Apply a lawn fungicide for brown patch in the early spring – May 1st – alternately at preventative rates 21-30 days apart – or according to the product label – will help prevent brown patch. More on alternative applications are below. 

Cultural Practices 

  • Use a sharp mower blade. Dull blades can tear and rip the grass, leaving is more susceptible to diseases
  • Avoid overwatering – fungus thrives in damp conditions. Twice per week at 1-1 1/2 inches of total water per week
  • Avoid watering overnight – extended periods of wet grass blades will increase likelihood of fungus
  • Water in early mornings – this will allow the water enough time to penetrate the soil, and excess water on the grass blades to evaporate in the later morning/early afternoon sun
  • When fungus is present, bag clippings and clean undercarriage of mower after each use

Fungus can become resistant to fungicides if the same fungicide is used too frequently, which is why we want to “apply fungicides alternately”. For example, if you only apply Scott’s DiseasEx which main active ingredient is Azoxystrobin (FRAC Group 11) then the brown patch can essentially become immune to this fungicide. Buy multiple products with different fungicides in different FRAC Groups to prevent fungicide resistance. 

The FRAC code is simply a combination of a number and/or letter which was assigned by the fungicide resistance action committee (FRAC). Active fungicide ingredients that target specific funguses and enzymes are grouped together to avoid the potential of resistance. And as previously mentioned, fungicides with the same FRAC code are at risk for disease and fungus resistance if used exclusively and continuously without rotation – for example Azoxystrobin and Fluoxastrobin in FRAC Group 11.

An example schedule of fungicide applications to avoid resistance. You may use all three, or a combination of any two:

  • First application: Scott’s DiseaseEx (Azoxystrobin, Group 11)
  • Second application: Quali-Pro 14.3 (Propiconazole, Group 3)
  • Third application: Clearys 3336F (Thiophanate Methyl, Group 1)
  • Repeat

Use our new Azoxystrobin calculator to help get the exact amount you need for your lawn.

Most of the fungicides are considered broad-spectrum fungicides, which means they are designed to manage a wide variety of diseases. Note that fungicides do not “kill” the fungus, but arrests the fungus. The fungicides will stop the growth and spreading of the disease, and help mitigate further damage, but will not repair what was done.

Fungicides to Prevent & Treat Brown Patch

While most fungicides below are broad-spectrum, these fungicides are particularly good at treating brown patch. The table below contains a list of fungicides types and popular fungicide products to help treat and prevent brown patch in your lawn. It is best to rotate the FRAC Groups in every other application, or no more than twice in a row. 

Bolded are recommended products after have been used by Lawn Phix and proven effective.

Quali-Pro 14.3 On Amazon

FRAC GROUP Fungicide Product Rates Duration
Group 1 Thiophanate Methyl Clearys 3336F 2-4  fl. oz. per 1,000 ft² 14 days
Group 3 Propiconazole Quali-Pro 14.3 1-2  fl. oz. per 1,000 ft² 14-21 days
Group 3 Myclobutanil Eagle 20EW 1.2 fl. oz. per 1,000 ft² 14 days
Group 11 Azoxystrobin Artavia 2SC 0.38-0.77 ounces per 1,000 ft² 14-28 days
Group 11 Azoxystrobin Heritage G 2-4 lbs.per 1,000 ft² 14-28 days

Note: This list is not exhaustive. There are more fungicides in some FRAC Groups that are not listed in the table above. Also note that some products such as Headway G contains active ingredients in multiple FRAC Groups (Axozystrobin in Group 11, and Propiconazole in Group 3).

If you’ve ever experienced lawn diseases such as brown patch, it’s not a pretty sight. This fungus can grow rapidly and decimate a lawn without the proper precautions. Follow these steps to prevent and treat brown patch for a green lawn and a successful growing season!


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Brown Patch FAQs

When should I first apply fungicide on my lawn?

The best action against lawn fungus and diseases is prevention. Your first preventive application of fungicide should be early Spring – around May 1.

What are the best fungicides for brown patch?

Products that contain Propiconazole (FRAC 3) and Azoxystrobin (FRAC 11) are two very effective fungicides for preventing and curing brown patch lawn disease. Quali-Pro Propiconazole 14.3, Heritage G, Azoxy 2SC, and Eagle 20EW (Myclobutanil) are several great products to choose from when dealing with brown patch.

How often should I apply fungicide to treat brown patch?

Always read the label of the products you’re applying. Generally for brown patch prevention, re-apply every 21-30 days at preventative rates. For curing brown patch, generally curative rates every 14-21 days apart.

What grass types are susceptible to brown patch fungus?

While most all cool-season grass types (KBG, perennial Ryegrass) and many warm-season grasses can become affected by brown patch, Tall Fescue that is the most common cool-season grass species that is most greatly susceptible and impacted by brown patch. Overseeding, particularly with a cool-season grass species diversity, can help heal and prevent brown patch disease. Common warm-season grass types that are affected by brown patch disease are Bermuda, Centipede, St. Augustine, and Zoysia.

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