5 Warning Signs Your Lawn Has Grubs (And How to Test for Them Today)
Maintaining a pristine, velvet-green lawn is a staple of American homeownership. It’s the backdrop for summer barbecues, a safe place for kids to play, and a significant contributor to your property's curb appeal. However, there is a silent threat lurking just inches beneath the surface that can turn your hard work into a patchwork of brown, dying turf.
If you have noticed your grass looking a bit lackluster lately, you might be dealing with a grub infestation. These white, C-shaped larvae—the offspring of various beetles—feast on the organic matter and root systems that keep your lawn healthy. Feeling frustrated when your watering and fertilizing routine fails to yield results is natural. The good news is that identifying the problem early can save your landscape from total devastation.
1. Strange Sponginess Underfoot
One of the earliest indicators of a subsurface issue is the texture of the ground itself. When you walk across a healthy lawn, the soil should feel firm and the grass resilient. If you begin to notice a "spongy" or "bouncy" sensation—almost like walking on a thick gym mat or loose carpet—it is a major red flag.
This sponginess occurs because the larvae have systematically detached the grass from its primary anchor: the soil. As they consume the root zone, the structural integrity of the turf collapses, leaving a layer of organic material sitting loosely on top of the dirt.
2. Irregular Brown Patches That Don't Recover
As the feeding intensifies, you will notice patches of your lawn turning yellow and eventually brown. At first, many homeowners mistake this for drought stress or a lack of nutrients. However, there is a key difference:
Drought Stress: Usually affects the entire lawn or areas in direct sun and recovers after deep watering.
Larvae Damage: Appears in irregular shapes and does not turn green no matter how much water or fertilizer you apply.
Because the roots are gone, the grass can no longer take up moisture, essentially causing the plant to wither from the bottom up despite the presence of water in the soil.
3. Increased Wildlife "Excavation"
Nature has its own way of signaling an infestation. If you notice that your yard has suddenly become a popular destination for local wildlife, you likely have a high protein source buried in your soil.
Raccoons, skunks, crows, and moles consider these larvae a gourmet delicacy. If you wake up to find small holes poked in the turf or entire sections of grass flipped over as if a small tiller went through it, these animals are hunting for the pests. While the animals are the ones doing the visible digging, the grubs are the "prize" that keeps them coming back.
4. The "Carpet Lift" Test
This is the most definitive way to confirm your suspicions without expensive equipment. Because these pests destroy the root system, the damaged turf loses its connection to the earth.
Choose a brown or thinning area of your lawn and firmly grasp a handful of grass. Pull straight up. If the section of turf lifts away from the soil with zero resistance—much like lifting a piece of old carpet or a rug—you have confirmed the presence of root-eating larvae. Upon lifting the grass, you will likely see the milky-white, C-shaped creatures curled up in the top two inches of the soil.
5. High Beetle Populations in Summer
While the larvae do the damage underground, the adults provide the warning. If you notice a heavy presence of Japanese Beetles, June Bugs, or Chafers buzzing around your porch lights or feeding on your ornamental plants during the summer months, they are likely using your lawn as a nursery.
These beetles burrow into moist, well-maintained lawns to lay their eggs. A high population of adult beetles in July almost certainly leads to a surge in larvae by late August and September.
How to Conduct a Professional-Grade Soil Audit
If you aren't sure whether your lawn needs treatment, you can perform a simple count to determine the "threshold of damage."
Select a Sample Area: Choose a one-square-foot section on the edge of a suspected brown patch.
Dig a Square: Using a spade, cut a square one foot wide and about three inches deep.
Count the Culprits: Sift through the soil and the grass roots carefully.
0–5 Larvae: This is considered a healthy level for most lawns; no action is usually needed.
6–9 Larvae: This is the "danger zone." A healthy lawn might survive, but a stressed lawn will show damage.
10+ Larvae: Immediate intervention is required to prevent widespread turf loss.
Effective Management and Restoration
Once you have identified the problem, the goal is to stop the cycle. Implementing a high-quality preventative treatment in the early summer can stop eggs from hatching. For active infestations in the fall, a curative treatment is necessary to knock down the population before they burrow deep for the winter.
Additionally, maintaining your grass at a height of 3 to 4 inches encourages deeper root growth, making the plants more resilient to minor feeding. Aerating your soil also helps by improving drainage and reducing the thatch layer where these pests thrive.
Protecting your outdoor investment starts with a keen eye. By catching these signs early, you ensure your lawn remains the envy of the neighborhood and a healthy space for your family to enjoy.