Protecting your grass from disease

Last Friday officially marked the first day of winter, but in deep South Texas the grass is still green and growing. Locally, we rarely get enough extended cold weather for our turf grasses to go into full dormancy. Turf grass issues, however, are still some of my most frequent questions.

In my short experience, fungal pathogens tend to be the most common in our area and seem to strike year round. As with most things, prevention is the best method to controlling the majority of these problems.

The first thing that you need to understand in preventing plant disease is the disease triangle. This fundamental concept states that three factors must be present for disease to occur in a plant; a susceptible host (plant), favorable conditions and the pathogen. Any two of these may be present in your yard, but once the third condition is met, disease strikes.

One of the most common turf grass diseases in our area is Take-All Root Rot (AKA Take-All Patch), caused by the fungus Gaeumannomyces graminis var. Both St. Augustine grass and Bermuda grass are severely affected by this pathogen. Initial symptoms begin as a yellowing of the grass, as the leaves die off the grass thins out exposing the dried and dying roots, nodes and stolons. It will continue to spread in irregular patches and if left unchecked can wipe out a whole yard.

Take-All Root Rot prefers high pH making it prevalent in our soils and once favorable conditions are present the disease is activated. This pathogen becomes active when there is excessive moisture and moderate temperatures, but can affect turf grass anytime during the year if the grass becomes stressed from drought, heat, shade, alkaline soil, or high-sodium water.

The first two things homeowners tend to do when the grass starts looking bad is put more water and mow the grass really short. These practices only worsen the problem, especially when dealing with fungal issues. During the winter months, days are shorter and temperatures are cooler so it’s important to adjust your watering schedule and mowing height to avoid stressing the grass and creating conditions favorable to fungal diseases.

Only water when necessary, if you can push your finger into the soil and feel moisture you don’t need to water. Increasing mowing height provides more surface area for photosynthesis and encourages deep root growth.

If you think your lawn might have a fungal disease, it’s highly recommended to submit a sample to the Texas Plant Disease Diagnostic Lab (https://plantclinic.tamu.edu/) for analysis before you begin a plan of treatment. Trying to remedy disease in the lawn can be costly, it’s best to know exactly what you are dealing with. There are fungicides that can help control these pathogens, unfortunately most of them are preventative and won’t do much once the symptoms have set in.

Even when they do control the fungal pathogen, they will do nothing to improve your damaged lawn. Prevention is key so here are a couple of resources to help you make the best management decisions for your lawn. Aggie Turf (https://aggieturf.tamu.edu/) is a great website for all things turf and this Earth-Kind video (https://aggie-horticulture.tamu.edu/earthkind/training/irrigation-system-auditing/) will show you how to perform an irrigation system audit to ensure you aren’t overwatering.

Ashley Gregory is the horticulturalist for Hidalgo County with Texas A&M AgriLife Extension Service. She can be reached at the Hidalgo County Extension Office at (956) 383-1026 or by email at ahgregory@ag.tamu.edu.