Weather is the key factor involved in sightings of Large Patch in some home lawns. The cool down expected for this weekend (since I am writing this in advance) will bring prime conditions for the start of Large Patch in local lawns. There are a few things that can be done to help keep the problem from worsening in you lawn.
I see Large Patch (aka Brown Patch) symptoms around the area every year with the arrival of the cold fronts that drop our nighttime temperatures in the mid to low 60’s. The fungus occupies lawns year-round. However, we only see the symptoms under certain conditions and certain times of the year. The fungus survives through the summer heat and then begins to thrive as temperatures ease in the fall and spring (70 degrees of below) and under wet conditions. Some years we can avoid flare-ups in the spring. Sometimes it is unavoidable because of the weather or micro-environments. I expect that we will see Large Patch either increase in size (if it is already present) or see new infestations in the next week or two. Especially with cool nights and humid conditions that are forecasted. The best way to know if you will be experiencing Large Patch, is to properly identify the patches and take notes of where the issue is and when it started to show up. My bet is, it typically will show up right after a cool-front drops temperatures into the 60’s and we get rainfall or are watering excessively.
If you have had this issue before or are experiencing it now, it is imperative to stay away from high nitrogen fertilizers and reduce your irrigation. I know we are getting close to fertilization time but either hold off or use a slow release or natural/organic fertilizer. For the Fall, I recommend fertilizing in September for the most part. Unfortunately, weather can vary from year to year and timing can change. For the Spring, I suggest fertilizing after April 1st most years. After April 15th seems to be better due to fact that lawns are typically actively growing at that point. If your lawn has exhibited symptoms of Large Patch in the past, then you would want to refrain from applying a fertilizer with too much readily available nitrogen. This is where I use the analogy of “it is like throwing gasoline on a fire.”
It just accelerates the fungal growth and damage a lawn severely. So, how do you choose a slow-release fertilizer? I would suggest using a fertilizer that has a minimum of ½ of the nitrogen in a slow-release form. Even better if the fertilizer is mostly slow release. This information it located on the fertilizer bag. Just remember not to apply more than 1 pound of actual nitrogen per year. Or, if you want to know exactly how much fertilizer to put out, have a soil test performed. Slow-release fertilizers provide fertility over a long period of time resulting in more a more consistent growth rate while reducing nitrogen run off and fungal problems.
In addition, check for low spots in the lawn. Those areas tend to be more susceptible to Large Patch because they harbor more humidity/moisture. Consider adding about ½ inch of a sandy loam or a compost to the low areas to improve drainage and level them out with the rest of the yard. Just be careful, adding more than the ½ inch of soil can smother the grass. In some cases, you may need to add more than ½ inch. If this is the case, then expect for the grass in that area to be very slow to recover or you may consider putting new sod down to cover the soil.
According to a Texas A&M AgriLife Extension publication, “The best protection by fungicides can be achieved when they are applied before disease symptoms appear. Fungicide efficacy is limited once the disease symptoms have occurred. Damaged grass will not recover until the following spring. Fungicide applications in the spring are not cost-effective.”
So, for the upcoming spring, keep in mind that the fungus will wane as environmental conditions become less favorable for fungal development. Just be on the lookout for Large Patch. If you know when and where Large Patch symptoms have shown up before, then you can try to use a fungicide as a preventative measure. Just remember fungicides are not curative. Hopefully this will shed some light on how to deal with Large Patch. Good Luck!
Don’t forget to send your garden questions to Plant Answers at 9020 Airport Rd., Conroe TX 77303 or e-mail me at mpotter@ag.tamu.edu.
