Whether your lawn is suffering from disease damage, insect damage, or something else, it is very likely related to moisture. Insects and diseases can attack your lawn if the proper conditions exist and your lawn is otherwise stressed. The first step in diagnosing any lawn problem should therefore begin with a moisture evaluation.
The easiest way to test for moisture in the soil is to perform the “probe test”. Find a long thin device (like a screwdriver or knife) that you can use to probe the soil. Push the probe into the soil, in both the brown problem areas and green areas. You should be able to easily push the probe into the soil 6 to 8 inches deep. If the problem area is more difficult to probe than the healthy area, the problem area is likely dry, and your lawn simply needs more water. In addition, if there is a drastic difference between the good and bad areas, your irrigation system may lack uniformity. At this point you should perform a uniformity test and modify your irrigation system as necessary.
If the problem areas probe easily, the lawn may be suffering from a fungal disease. There are different types of fungi that require differing specific conditions for survival. In general, however, they thrive in moist warm environments, and cannot survive if either these components are not met. While we cannot effect the temperature, soil moisture is in our control. As a result, the most effective method of disease control is to modify your irrigation schedule.
Study the section on irrigation carefully. Once your lawn is established, you should not have to irrigate more than once every second or third day. In addition, you should avoid watering your lawn during the afternoon or evening hours. Following these general rules will allow the lawn blades and soil surface to dry between irrigations, breaking the cycle for disease development.
In some instances, your lawn may be suffering from an insect infestation. In general, insects, like fungi, are more active in warm moist conditions. Like fungi, control starts with irrigation. Follow the recommendations above carefully. If you need more information read our lawn watering discussion.
While most insects are not harmful to your turf, some like the sod web worm, cut worm, and chinch bug (primarily St. Augustine), can be detrimental. To detect these insects, mix 1 to 2 ounces of dishwashing liquid with one gallon of water and apply it evenly to a square yard of turf with a sprinkle can. After 5 to 10 minutes, the insects should move to the surface, where you can collect them. Place the insects into a bag and bring them in to your local nurseryman for identification or refer to the University Cooperative Extension Pest Management Guidelines.
If you have determined that your lawn is suffering from disease or insects, and you are confident that your irrigation program is correct, you may choose to purchase an appropriate insecticide or fungicide to help ensure control. Be sure to read the label carefully and apply the chemical as recommended.