Variety of issues plague St. Augustine lawns

By Todd Vineyard | Published Wednesday, May 9, 2018

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The loss of St. Augustine grass in Texas lawns is observed during the summer and fall months every year and those problems can linger into the spring.

While other turfgrasses are affected, lawns with St. Augustine seem to be hit the hardest. This year we are seeing lawns affected by drought and freezing temperatures.

If not watered during the winter months, many lawns will not have enough soil moisture during the freezing temperatures, exposing root zones to freeze damage.

One of the problems I encounter in St. Augustine lawns each spring is yellowing or chlorasis. At first, it appears to be an iron deficiency, but applications of iron don’t always correct the problem. The chlorosis may be due to a combination of factors, including lack of iron and nitrogen and St. Augustine Decline (SAD). SAD is a virus that produces a chlorotic mottling affect that is often mistaken for iron chlorosis. I have come to the conclusion that most St. Augustine lawns are going to have some yellowing almost every year.

Using management practices for maintenance of St. Augustine lawns is one of the best things a homeowner can do to prevent stress to the lawn.

Many of the problems associated with the loss of St. Augustine turf are due to stress. While we can’t control the weather, managing the St. Augustine lawn properly will help reduce plant loss during periods of weather-related stress.

St. Augustine requires more water than other varieties of grass. Homeowners should evaluate the way they water their lawns. Deep watering will allow grasses to develop deeper and healthier root systems.

Fertilization is always key to maintaining healthy landscapes. The recommended rate of nitrogen for St. Augustine grass in full sun is 3 to 4 pounds per 1,000 square feet. For shade areas, the recommended rate is 1 to 2 pounds per 1,000 square feet.

Rates of phosphorous and potassium should be determined by a soil test.

Apply the first application after the lawn has been mowed a couple of times in the spring. For grass growing in full sun, fertilize once in the summer and again in the fall. Shady areas should be fertilized once in the spring and once in the fall.

Another common problem in St. Augustine lawns is brown patch. Normally this disease shows up in the fall, but it has been reported in St Augustine lawns throughout Texas in the spring.

There are several fungicides available locally for brown patch control. While brown patch doesn’t normally kill affected plants, it can weaken the affected area and make them more susceptible to other stress problems. Close observation of the affected area reveals leaves with a rotted sheath.

Take All Root Rot (TARR) can also be a major contributor to problems in St. Augustine lawns. This fungus attacks the root system primarily in the fall and spring months when soil temperatures are in the 60 to 65 degree range. Any factor that causes stress to the turf will enhance the potential for TARR to become a problem. TARR is characterized by brown leaf blades that are firmly attached, brown stolons and a shortened root system that is brown to black in color. Control can be difficult. Approved fungicides may help. Topdressing the affected areas with sphagnum peat moss has also provided some control. Peat moss must be watered in thoroughly to be effective.

New homeowners looking to establish a home lawn need to select a grass that will be suited to the growing conditions in North Texas.

Todd Vineyard is a Wise County Extension agent.

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