A drench test can be performed to detect the presence of adult and larval insects that feed below the soil surface. Mix 1 to 2 fluid ounces (2 – 4 tablespoons) of liquid dish soap to a gallon of water. Two gallons of water may be necessary where soils are dry.

Test an area of the lawn that includes both healthy and unhealthy grass. Mark one square yard of lawn off with a piece of rope and apply the solution as evenly as possible over the area with a sprinkling can. The soap solution will cause insects to move to the surface. Identify and count the presence of any insects within ten minutes of performing the test.