I have looked at multiple yards this summer that all have the same problem, and it doesn’t matter where in the county I go. The problem appears to be take-all root rot, or take-all patch. This disease, left unchecked, can cause devastating effects to your lawn turf.
Take-all root rot is a fungal disease that causes weak, brown, dead patches in turfgrass. In Texas, the disease severely affects St. Augustine grass and Bermuda grass, in which the disease is known as Bermuda grass decline.
Take-all root rot is caused by a fungus, Gaeumannomyces graminis var. graminis, that lives in the soil. The fungus lives in many parts of Texas and is commonly found in both diseased-looking and apparently healthy turfgrass. It lives in thatch, which is a layer of plant roots, stolons (shoots that grow horizontally along the ground surface) and decaying plant matter.
The symptoms of take-all root rot often appear in spring or early summer, when the turfgrass emerges from winter dormancy. However, they may appear anytime during the growing season when the grass is stressed by heat, drought, shade, alkaline soil or high-sodium water.
The most obvious initial symptom is yellowish foliage that eventually turns brown and wilts. The turf thins out, leaving brown, irregular patches from 1 foot to more than 20 feet in diameter. As a field diagnosis, look at the roots of infected grass, which are usually short, blackened and rotten, making it easy to lift the stolons from the soil. The nodes, or stem joints, may be discolored.
To prevent take-all root rot, the most effective approach is to take proper care of the grass. The disease usually becomes a serious problem when the turfgrass is under stress because of unfavorable environmental conditions and improper management: excessive shade, herbicide injury, soil compaction, temperature extremes, imbalanced soil fertility, inappropriate irrigation scheduling, improper mowing height or frequency or any other condition that weakens the turf.
Encourage healthy root development as much as possible. Make sure the area drains well at and below the soil surface. Turf areas that remain wet are prone to the disease. Improve the drainage and avoid overwatering.
Control and Management
To reduce take-all root rot, lower the soil pH to a range of about neutral to slightly acidic levels, if practical. Some soils can be slowly acidified over years by continual applications of ammonium sulfate, powdered sulfur (3-5 pounds per 1,000 square feet per year) mixed with well-decomposed compost or sphagnum peat moss (1 to 2 bales per 1,000 square feet per application; each bale is 3.8 cubic feet; make 1 to 2 applications per year).
Be judicious and apply ammonium sulfate – or any other quick-release soluble nitrogen – at a rate no higher than 1 pound of nitrogen per 1,000 square feet per application. For St. Augustine grass, apply no more than 4 pounds of nitrogen fertilizer per 1,000 square feet per year. For Bermuda grass, apply no more than 5 pounds per 1,000 square feet per year.
Once take-all root rot has infested a lawn, you will probably need to apply fungicide as well as adopt proper cultural practices, such as mowing and watering.
The best times to apply fungicides are spring and fall. Mix the fungicide with plenty of water (4 to 5 gallons of water per 1,000 square feet) and thoroughly water the grass immediately after application (¼ to ½ inch water). The water will ensure the product moves into the grass stolon and root zone rather than drying on the leaves. To help the fungicide reach the soil, rake and remove any infected or dead plant materials before application. Fungicides are best used as preventive measures before symptoms develop. Always read and carefully follow the instructions and precautions on the product label.
Hopefully, you can get this disease under control before it causes huge dead and bare-looking spots in your lawn landscape. Please call the Victoria County Extension Office at 361-575-4581 with questions. Let it rain!
SOURCE: Take-All Root Root Publication, E-615, Texas A&M Agrilife Extension, Young-ki Jo Assistant Professor and Extension Plant Pathology Specialist