Large Patch Fungus
Horticulture Hotline 11/25/23
By Bill Lamson-Scribner
We finally got some much-needed rain and here comes the disease that attacks the turf while it is going into dormancy (fall) or coming of dormancy (spring). 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. 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? Be sure the areas that are brown are your turfgrass and not summer annual weeds (crabgrass...) that have died (doubtfully if a reader of the Horticulture Hotline).
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.
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.
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 if you see that the weather is warming. 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. Treating preventatively requires less product and less frequent applications of fungicides.
A good granular one-two punch control strategy is T-Methyl and Strobe Pro G (both 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. If you do not manage the disease, the grass will thin and weeds will take over.
What an awesome Lowcountry Fall! James Island County Park’s Holiday Festival of Lights? Soil Test and Fertility Program from Possum’s? Rats? Roaches? Fleas? Tree pruning and trimming? Transplant shrubs or trees? Edge bed lines and sidewalks for the last time for a while? Rake or blow leaves? Clean out beds that have an accumulation of mulch, leaves, or pine straw?
Always read, understand, and follow product label. The product label is a Federal Law.
