Signs your lawn has grass destroying grubs, and what to do about it

Grub activity, especially Billbugs and white grubs, is common in Colorado and can lead to irregular brown patches in the lawn.

Lawn grubs, the larval stage of various beetle species, can significantly damage lawns in Colorado by feeding on the roots, causing them to be easily pulled up.  Grubs are most active in late summer and early fall. 

Signs that your lawn has grubs include:

• Brown or dying patches that lift easily like a carpet, revealing white, C-shaped grubs in the soil underneath.
  
  
• Spongy feel underfoot, especially in early morning or after watering.
• Increased animal activity—birds, skunks, raccoons, or moles digging up your lawn to eat the grubs.
• Wilting grass that doesn’t respond to watering, as grubs chew through grassroots.
• Thinning turf in irregular patterns, often starting in late summer or early fall.

If you suspect grubs, try the “tug test”: grab a handful of grass and pull gently—if it comes up with little resistance and no roots, grubs may be the culprit.

Fix a lawn grub problem by following these steps:

1. Confirm the Infestation

• Dig a square foot section of turf (about 2–4 inches deep) in suspected areas.
• If you find 6 or more grubs per square foot, treatment is likely needed.

2. Choose a Treatment Method👉 Chemical Options:

• Curative treatments (like products with carbaryl or trichlorfon) work best in late summer to early fall, when grubs are small and feeding near the surface.
• Preventive treatments (like those with imidacloprid or chlorantraniliprole) are applied in spring to early summer to stop future infestations.

Natural Solutions:

• Milky spore or beneficial nematodes (Heterorhabditis bacteriophora) can control grubs biologically, though results may take longer.
• Apply when soil is warm and moist—typically late spring through early fall.

3. Water Smart

• Water the lawn after applying most treatments to help carry them into the soil where grubs live (follow package directions).

4. Repair Lawn Damage

• Rake out dead patches and reseed or patch the lawn in early fall or spring.
• Aerate compacted areas and feed with a balanced lawn fertilizer to encourage healthy regrowth.

Here's another article that addresses lawn grubs and solutions for fixing the problem.