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How to Manage Pests

The UC Guide to Healthy Lawns

Drench test

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.

A marked off area for a drench test

Performing a drench test

Treatment thresholds for insects
detected with the drench test
Pest*
Treatment threshold
Cutworm larva
Armyworms, cutworms
5/yd2
Fiery skipper larva
Fiery skipper larvae
15/yd2
Sod webworms
Sod webworms
15/yd2
Southern chinch bug adult
Southern chinch bugs
135/yd2 or
15 nymphs and adults/ft2

*White grubs and billbug larvae are monitored through digging.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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Agriculture and Natural Resources, University of California

Accessibility   /TOOLS/TURF/PESTS/indrench.html revised: July 10, 2014. Contact webmaster.