Grub Damage vs. Drought: How to Tell the Difference in Your Lawn

Brown, patchy grass is a common sight in late summer—but what’s really behind it? While drought is often the go-to explanation, it’s not always the culprit. In many cases, white grubs are to blame, quietly feeding on grassroots beneath the surface. Knowing the difference between grub damage and drought stress is key to saving your lawn and applying the right treatment.

Let’s break down how to spot the signs and what to do next.

What Are Grubs and Why Are They a Problem?

Grubs are the larvae of beetles like Japanese beetles, June bugs, and chafer beetles. These small, white, C-shaped insects live just below the soil surface and feast on the roots of your grass. Without healthy roots, grass can’t absorb water and nutrients properly, leading to dead patches.

Grub problems tend to surface in late summer through early fall, when the larvae are most actively feeding.

Signs of Grub Damage in Lawns

Wondering if grubs are the cause of your brown lawn? Look for these telltale signs:

• Patchy Brown Spots: Irregular dead patches that expand over time.
• Spongy Turf: Affected areas feel soft underfoot, almost like walking on a sponge.
• Grass Pulls Up Easily: You can tug up damaged turf like a carpet, with little resistance.
• Visible Grubs: Underneath the damaged turf, you may spot white, C-shaped grubs.
• Animal Digging: Birds, raccoons, and skunks may dig up your yard looking for a grub snack.

Signs of Drought Stress in Lawns

Drought stress also causes browning, but the symptoms are different:

• Uniform Browning: Large areas of the lawn may turn brown, especially in sunny spots.
• Dry Soil: The soil is hard and cracked, with little moisture.
• Grass Blade Curling: Grass often turns gray-blue before browning and curls in on itself.
• Firmly Rooted Grass: Even though it’s brown, the grass doesn’t lift up easily.
• No Animal Activity: There's no digging or sign of pests in the soil.

Grub Damage vs. Drought Stress: Key Differences

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How to Confirm Grub Damage

You don’t have to guess—grab a small shovel and inspect your lawn:

1. Choose a brown patch and cut a square foot of turf about 2–4 inches deep.
2. Gently peel it back and inspect the soil for white grubs.
3. If you find more than 5–10 grubs per square foot, you likely have a problem worth treating.

Treatment Options for Grubs

If you’ve confirmed grub activity, act fast:

• Curative Treatments: Products with carbaryl or trichlorfon can kill active grubs.
• Preventive Treatments: Apply imidacloprid or chlorantraniliprole in spring or early summer to stop future infestations.
• Natural Options: Beneficial nematodes and milky spore disease are organic solutions that target grubs without harming the environment.

For the best results, we suggest you consult a professional.

Tips to Prevent Future Lawn Issues

• Aerate and overseed in the fall to promote healthy turf growth.
• Water deeply but infrequently to encourage deep root systems.
• Avoid overwatering—too much moisture can attract beetles looking to lay eggs.
• Apply grub preventers annually if grubs are a recurring problem in your area.

Contact A PA Lawn Expert

When your lawn starts turning brown, it’s easy to assume the summer sun is to blame. But grubs may be the real culprits—silently chewing away at your grass from below. Learning how to tell the difference between grub damage and drought stress will help you take the right action and keep your lawn healthy year-round.

Still unsure what’s causing the damage? Contact Lawn Sense for a thorough inspection and treatment plan. The sooner you act, the better your chances of saving your lawn.