Horticulture Hotline 10/11/21
By Bill Lamson-Scribner
While walking and driving around, it seems that brown patch/ large patch/ Zoysia patch (I will use these names interchangeable) has invaded the Lowcountry in a big way. As the cooler weather comes and the grass growth rate slows down, large patch / brown patch / zoysia patch fungus began to show up in our lawns. Does it seem to you that right when we got the army worms and sod web worms under control, here comes the large patch? Proving once again, the Lowcountry is the hardest place in the world to grow grass and why it is so important to have a program for your lawn. Do you see areas of your grass that are brown when other parts are green?
Large patch disease is always present in the lawn, it just manifests itself when the environmental conditions are right and your grass cannot outgrow the damage. Without any sustained cold temperatures, this disease is slowly spreading across lawns as the temperatures that favor its growth keep coming into play. This prolonged fall is great for outdoor activities like visiting local plantations, fishing, boating, golfing, shopping and working in the yard; however, the temperatures are also perfect for these diseases to develop. The grass is not fully actively growing (not mowing as much) and it is not fully dormant (brown), so these are perfect conditions for the disease to attack.
Since this disease is a big problem in the Lowcountry, knowing that it is a soil borne disease can help you with control strategies. Being a soil borne disease, you know that it will reoccur in the same areas year after year. There are not any spores flying through the air like many of your leaf spot fungi, so the disease is easier to control.
As a soil borne fungus, if you map the areas that you have the disease, you can concentrate your control efforts (dollars) into a smaller area, putting less control products into the environment. If your yard is 5,000 sq ft usually you might have a few infected areas which might total approx. 500 ft. Instead of using control products to treat 5,000 sq ft, you can concentrate your efforts into the 500 ft (i.e. 10% of your total yard). If Large Patch was an air borne fungus with spores, you would have to treat the entire yard because air borne fungi spreads a lot quicker than soil borne fungi.
As your grass is going into dormancy and the temperatures begin to cool at night, large patch is ready to attack your grass. Large patch will go inactive when the temperatures get very cold; however, it will become active again when the temperatures favor the disease. If you have discolored areas in your yard that appear to be a disease, check with someone that knows. Even if it is during a cold phase and the disease does not appear to be active, you can still put out a systemic fungicide for protection. Our soils do not get so cold that the plant will not absorb the fungicide with its roots. Remember treating a fungus with a systemic fungicide is like getting a flu shot – you do it preventatively before you have the disease. If it is too late to use it preventively, when you want the disease to stop spreading, you can use the fungicide curatively.
A good granular one-two punch control strategy is T-Methyl and Strobe Pro G (all systemic fungicides that get into the plant). Use these products in areas where you have had Large Patch previously at the preventive rates and intervals recommended on the labels. Be sure to use T-Methyl with Strobe Pro G, so you are switching chemistry classes and modes of action. Good control early on can help avoid flare ups in the spring also.
Large patch usually likes wet, heavy thatch, improper nutrition, and/or compacted soils. Culturally you need to manage your irrigation system, raise any low areas, and correct drainage problems. Reducing thatch (at Possum’s we have a great organic granular product for controlling thatch), maintaining proper fertility levels, and aerating to alleviate compaction, will also help control large patch. A healthy turf (following soil test derived feeding schedule) with a soil with a lot of bio-diversity (use of cotton burr compost, SeaHume and other organics) has shown to help manage this disease.
It is a great time to apply Wet & Forget for a little fall cleaning. Great product unless you are in the dog house for something or need immediate results. You spray the product then it slowly starts cleaning. In two weeks, you usually can see a big difference, and it continues to clean for a while afterwards.
Time to take soil test. Every soil test is unique to your yard. Time to get ready for 2022.
Always read, understand and follow product label. The product label is a Federal Law.
