Guide · Insects
Grubs: how to tell, and when to treat
Most lawns never need grub control. The ones that do need it at the right time.
What they are
Lawn grubs are the C-shaped, cream-colored larvae of beetles: Japanese beetles, masked chafers, European chafers and May/June beetles. Adults lay eggs in the lawn in early to mid summer, the young grubs feed on roots through late summer and fall, go deep for winter, then feed briefly again in spring.
Signs of grub damage
- Irregular brown patches in late summer or early fall that don't green up after watering.
- The turf peels back like a loose carpet because the roots are gone.
- Skunks, raccoons, armadillos or birds tearing up the lawn overnight. They're digging for grubs.
Count before you treat
Cut three sides of a 1 ft × 1 ft square about 2 inches deep, fold the sod back, and count the grubs in the soil and roots. Check a few spots at the edge of the damage.
| Grubs per sq ft | What it means |
|---|---|
| 0–5 | Normal. A healthy lawn handles this. Don't treat. |
| 6–10 | Borderline. Treat if the lawn is already stressed, or if animals are digging. |
| 10+ | Treat. |
Two ways to control them
Preventive: spring to early summer, before the eggs hatch
For lawns with a history of grub damage. It goes down before you can see a problem and stops the new generation as it hatches.
- Chlorantraniliprole (Acelepryn, Scotts GrubEx1): apply April to May. Its long residual covers the summer hatch, and it's very low-risk to bees and other pollinators. This is our first choice.
- Imidacloprid and other neonicotinoids: apply June to mid-July. Effective, but mow off any flowering clover or dandelions first, since these products are toxic to bees.
Water preventives in with about ½ inch so they reach the root zone.
Curative: late summer to early fall, when you've counted 10+
- Trichlorfon (Dylox) works in days on young grubs. Apply in August to September and water in with ½ inch right away.
- Spring treatment of large, overwintered grubs is rarely worth it: they're hard to kill and about to stop feeding anyway.
Biological options
- Beneficial nematodes (Heterorhabditis) can work on young grubs in late summer, if the soil stays moist.
- Btg (Bacillus thuringiensis galleriae) products target beetle larvae specifically.
- Milky spore only affects Japanese beetle grubs and takes years to build up. It's not a quick fix.
Moles aren't a grub problem
Moles mostly eat earthworms. Killing every grub rarely makes moles leave.
Fix the damage
Rake out dead turf. For cool-season grass, overseed in early fall. For warm-season grass, let it spread back in, or patch with sod or plugs in late spring.
Always follow the label. The label is the law for rates, timing and re-entry, and some products aren't registered in every state.
The Lawn Obsessed USA app puts grub prevention on the calendar for your region and grass, with the products and the watering-in reminder.