Make Sure Lawn Disease Is Actually a Disease

Q. I have never had fungus in my front or back lawn for decades. My front yard is good, but my backyard is absolutely horrid now. I had a clock problem but I never water during the night. I sprayed a fungicide and it did not help. Everyone tells me the fungus will always be there and continue to cause problems. I am concerned about the cost of continually buying and spraying fungicides in the future. 

A. Three problems cause lawns to fail; irrigation, disease and insects. By far, the majority of problems in the desert are irrigation problems. Without irrigation, lawns cannot exist. The reason for a lawn browning, however, can easily be misidentified.

            I follow a three-step process in lawn problem identification that relies on the elimination of problems in this order; insect, irrigation and finally disease.

            Insect problems are the easiest to identify between the three. Insect damage to a lawn may not follow any type of visual pattern because they usually involve some sort of “eating” of the roots, stems or leaves. Lightly pulling on damaged grass that neighbors dead areas usually reveals if it is insect damage.

            Irrigation. Browning of the lawn because of inadequate irrigation usually resembles the irrigation pattern. Identifying where the sprinkler heads are located, and then identifying the pattern of damage, oftentimes confirms if the damage is related to irrigation. Sometimes looking at individual blades of grass reveals tip burn or dieback from a lack of water.

            Disease. Browning from diseases may or may not follow a pattern depending on the disease and are the most difficult to identify. In the case of diseases, the only sure way is to send a sample to a pathologist but by the time you get the results it’s too late.

            Another way is to apply a fungicide. If the disease stops then it’s possible, but not always correct, the problem was caused by a disease. Browning of the grass caused by diseases can reveal some very interesting patterns when it is first starting. These patterns might be circular brown damage with a green center (frogeye) or in the shape of horseshoes, or no pattern at all.

            Looking for disease problems usually involves getting on your knees and looking at individual blades of grass growing closely to the brown area. Sometimes spotting or discoloration of individual blades of grass may indicate the presence of a disease.

            In any case, spraying a fungicide when insects or irrigation are the problem will not correct it. Go through this three-step method first before jumping to a conclusion about a disease problem and applying pesticides.