Skip to main content

Brown Patch

Home > Resources > Brown Patch

What is Brown Patch?

Rhizoctonia Blight or the more commonly known name of Brown Patch disease is a hot weather disease that can occur on all types of North Texas turf; however, it is most damaging to St Augustine, but can affect Zoysia grass too. You tend to see injury in late summer when the nighttime temperatures begin to decrease. Brown Patch often first appears as rough circular patches varying roughly in size from 1-5 feet. 


In the early morning hours, fine strands of grayish cobwebby fungal growth called mycelium may be evident (pictured below) – it will appear as dew on the lawn. This quickly disappears as the mycelium dries or if you touch it. Individual leaves on the turf die back from the tip and can turn dark green, then yellow as they wither and decay.
 

Brown Patch is caused by infection of grass foliage and crowns by Rhizoctonia fungi. Rhizoctonia fungi often harmlessly colonize organic matter into thatch; however, during times of stressful conditions Brown Patch can infect your North Texas lawn and cause disease.
 

Conditions Favoring Brown Patch Disease

The conditions that favor Brown Patch development in warm season grasses are when temperatures begin to decrease after the hot summer months. A minimum temperature of 61 F in combination with evening showers, or night time watering, or relative humidity above 95% for more than 8 hours increases the chances of Brown Patch developing in the lawn. In warm season grasses, injury due to Brown Patch is most severe in humid weather or lawns that are frequently watered, with moderate temperatures (45-70 F). 
 

Management of the Disease

There are several actions you can take to properly control and help prevent this disease from developing in your lawn:


1. Proper Mowing: This is extremely critical!  St Augustine grass should always be mowed at 3” height.  Mowing it any shorter stresses the plant creating a situation for the disease to develop.

Mow with a sharp blade!  A dull blade rips the leaves making it harder to heal and susceptible for disease to develop.  Compare this to cutting your finger with a sharp smooth knife vs. a dull serrated knife.  The cut from a sharp smooth knife will heal rather quickly, whereas the cut from the dull serrated knife will take longer with redness normally occurring around the cut.                                      

Inspect your lawn after each mowing to ensure clean smooth cuts of the blades.  If you lawn is mowed by a service, check several areas of the lawn as they may have used more than one mower to cut your grass.  Do not hesitate to contact the service mowing your lawn, they may not be aware of the importance of always using sharp blades on St Augustine lawns.

2. Proper Watering: Even during the hot summer months, you should only water twice a week at 3-4 day intervals.  Fungus spores activate with water and it takes 2-3 days of no additional water for the spores to die from the sun and wind.  If you are watering more frequently than 3-4 day intervals, you are keeping the spores active and fostering the conditions for the grass to become infected.

3. Watchful Eye: The amount of time it takes from when the yellowing appears and the leaves turn brown is about 2-4 weeks.  Our most difficult challenge is that we perform applications at 7-8 week intervals during the time of year this situation usually occurs.  It is very easy for us to miss seeing the problem because the situation was not present during the treatment performed in Aug/Sep, then the lawn is transitioning into dormancy when we return for the next scheduled application 7-8 weeks later.  The yellowing is likely no longer occurring with the majority of the lawn going into dormancy, which makes the brown leaves look like the typical signs of going into dormancy.                    
If you see yellowing of the leaves beginning to occur, typically after Labor Day, call us immediately!  If this situation is not addressed quickly, it will be spring before the problem is noticed when the brown leaves fail to turn green as the lawn transitions out of dormancy.  At this point it is too late to do anything but see if the lawn will recover on its own through warmer temperatures, fertilizing and mowing.  In severe situations, the only option is to install new sod.

4. Annual Disease Control treatments: If you have St Augustine grass, you need to be on the annual schedule for this application.  We apply the treatment at the best time each year before the disease typically appears.  The actual time of year this is applied varies from early Aug to mid Sep, it is determined by the weather conditions each year.  Our intent is to apply the application 1-2 weeks before the disease normally appears, this significantly reduces the chance of developing the disease.  Occasionally, a lawn might show a slight appearance of the disease after this treatment but causes little to no damage to the lawn.
 

Weed Man North DFW Can Help

Weed Man North DFW is here to help. Weed Man North DFW's turf specialists can recognize Brown Patch and make recommendations to help you prevent the disease or help the lawn recover. Weed Man's specially blended slow release fertilizer applied at the right time is the first step in preventing Brown Patch. Weed Man's fertilizer helps create healthy turf by slowly feeding the lawn as it needs it encouraging deep rooting systems that will survive and recover more quickly when cooler weather arrives. Weed Man North DFW can offer advice on future treatments that may be necessary to help your turf remain healthy during times of Brown Patch activity.