Army worms can move through a lawn or field with frightening speed, leaving behind dead, discolored turf in their wake. Identifying an infestation early is the difference between a quick recovery and a total replant. Effective scouting requires a combination of visual inspection, simple field tests, and an understanding of the pest’s life cycle.
Understanding Army Worm Behavior
Before learning how to check for army worms, it helps to understand what you are looking for. These pests are most active during the cooler hours of the early morning and late evening, feeding on grass blades before retreating to the soil during the heat of the day. They are often brought into a yard by wind currents, meaning damage can appear suddenly and spread quickly across large areas.
Visual Inspection of the Grass
The most immediate way to check for army worms is to look at the grass itself. Unlike drought stress, which usually causes a general yellowing, army worm damage appears as irregular brown patches that spread outward. You should look for grass that feels thin or see-through, as the larvae strip the green tissue away while leaving the stems alone.
The Soap Flush Test
If the visual signs are unclear, the soap flush test is a reliable method to confirm the presence of army worms. Mix two tablespoons of liquid dish soap with two gallons of water and pour the mixture evenly over a square foot of grass. The soap irritates the insects, forcing them to the surface within minutes. If army worms are present, you will see them curling up on the surface of the wet grass.
Checking the Thatch and Soil
Army worms do not live exclusively in the grass blades; they rest in the thatch and soil during the day. To check these areas, use a spade to cut a square foot section of turf about two inches deep. Peel back the grass to inspect the soil and the white thatch layer. Look for small, green caterpillars or dark spots where they may be hiding. Disturbing the soil lightly with a stick can encourage them to move, making them easier to spot.
Signs of Damage and Life Cycle
Recognizing the stages of damage helps you determine how urgent the threat is. Early signs include surface feeding, which creates a grayish cast across the lawn. As the larvae mature, they develop stripes down their sides and grow rapidly. They eventually burrow into the soil to form a cocoon, so seeing adult moths flying low over the grass at dusk is often the first indicator that eggs will soon hatch.
Tools and Equipment for Detection
While you do not need specialized tools, having the right equipment makes the inspection process more efficient. A standard garden hose is necessary for the soap flush test, while a small spade or trowel is essential for examining the thatch. A flashlight is useful if you are checking for nocturnal activity or inspecting the lawn early in the morning before the sun rises fully.
When to Call a Professional
If your property is large or the damage is spreading quickly, you may need professional assistance. Pest control experts have access to more potent insecticides and monitoring equipment that are not available to the general public. They can also provide a detailed assessment to ensure that the problem is indeed army worms and not another type of turf pest.
