How do you get rid of grubs in your lawn?
Short answer: Confirm grubs first: Purdue says fewer than 5 grubs per square foot rarely need treatment; Japanese beetle grubs usually need 10 or more, European chafer as few as 5. Apply a preventive insecticide such as chlorantraniliprole or imidacloprid around late June to mid-July. For damage found later, a curative product such as trichlorfon works faster. Water it in and follow the label.
What are the signs of grubs in a lawn?
White grubs are beetle larvae that feed on turfgrass roots. Damage usually shows as wilting that watering does not fix. Purdue and Nebraska Extension list these signs:
- Patchy areas of wilting turf that do not respond to irrigation
- A blue or purple cast before the grass collapses into dead or thin patches
- Pale, discolored grass that looks drought-stressed
- Turf that feels spongy and lifts or rolls back like a carpet
- Grubs visible in the soil when you pull the sod up
- Raccoons, skunks, turkeys or moles digging small patches to feed on grubs
Animal digging is often the first clue. If moles are the main problem, see how to get rid of moles in your yard.
How many grubs per square foot before you treat?
Count before you buy anything. A practical method is to cut a 1-foot square of sod a few inches deep, peel it back, and count the grubs. Check several spots, in damaged areas and at their edges.
Purdue’s thresholds depend on the species:
| Grubs per sq ft | Purdue guidance |
|---|---|
| Fewer than 5 | Rarely require treatment |
| 5 | European chafer can cause damage |
| 10 or more | Usually required for Japanese beetle, Asiatic garden beetle and black turfgrass ataenius |
| As high as 20 | May not necessarily cause noticeable damage |
Purdue notes green June beetle grubs can cause unacceptable damage at even lower densities. Nebraska Extension says more than 8-10 masked chafer grubs or 3-5 May/June beetle grubs per square foot warrant treatment.
To average your samples: total grubs ÷ number of 1-ft² samples. For example, 6 + 14 + 10 = 30 grubs in 3 samples is 10 per sq ft.
When should you apply grub control?
There are two strategies. Preventive products go down before eggs hatch. Curative products kill grubs that are already feeding.
| Strategy | Timing (as sourced) | Notes |
|---|---|---|
| Preventive | Early to mid-July is “almost always optimum” (Purdue, Indiana). Third week of June through early July (Nebraska). | Product is in the soil when eggs hatch |
| Early curative | After egg hatch, before damage is visible | Relies on sampling grubs in the soil first (Purdue) |
| Late curative (rescue) | After damage appears; Nebraska cites about the first week of August | Works less well once grubs stop feeding or move deeper for winter |
Exact timing varies by region and beetle species. Your state extension office can give local dates.
Which grub killer ingredients work?
Purdue’s table matches active ingredients to strategies (common examples shown):
| Active ingredient | Class | Preventive | Early curative | Late curative |
|---|---|---|---|---|
| Chlorantraniliprole | Diamide | Yes | Yes | No |
| Imidacloprid | Neonicotinoid | Yes | Yes | Yes |
| Trichlorfon | Organophosphate | No | Yes | Yes |
| Carbaryl | Carbamate | No | Yes | Yes |
Chlorantraniliprole is a preventive (and early curative) choice. Trichlorfon and carbaryl are curative only. Purdue also lists clothianidin and thiamethoxam (all three timings) and cyantraniliprole and tetraniliprole (preventive and early curative). Check the label for the active ingredient, not just the brand name.
Even registered products are not perfect. Nebraska Extension says they usually kill 75-90% of grubs. Very high populations may need a second application.
Do you need to water in grub control?
Yes, for most products. Purdue recommends irrigation or rainfall after chemical applications to wash the insecticide into the soil. Nebraska Extension says to apply at least 1/2 to 3/4 inch of water.
If you use beneficial nematodes (Heterorhabditis bacteriophora), Purdue says irrigation should immediately follow application to wash them into the soil.
How do you protect bees when treating grubs?
Mow first. Cornell Cooperative Extension advises mowing to remove weed flowers before any lawn grub application. Cornell notes the most widely used grub products are neonicotinoids, which are toxic to pollinators if sprayed over flowers.
- Mow off flowering weeds in and around the treated area.
- Never spray plants in bloom or about to bloom.
- Avoid drift onto nearby flowers.
If the lawn is mowed first or has no flowers, Cornell says grub products are unlikely to harm bees unless spray drifts onto flowers.
Safety and the label
Purdue’s advice is to read and follow all label instructions, including hazard and environmental precautions.
- Keep children and pets off treated areas for the time the label states.
- Wear the protective gear listed on the label.
Quick answers
What month should I put down grub killer? For preventive products, late June to mid-July in Indiana and Nebraska, per Purdue and Nebraska Extension. Curative products go down when grubs are present and feeding; Nebraska cites early August.
How many grubs per square foot is too many? Purdue says fewer than 5 rarely need treatment. Japanese beetle and similar grubs usually need 10 or more per square foot; European chafer can do damage at 5.
What kills grubs fast? Curative insecticides such as trichlorfon or carbaryl target grubs already in the soil. Water them in as the label directs.
Is chlorantraniliprole preventive or curative? Purdue lists it for preventive and early curative use, not late curative rescue.
Why are animals digging up my lawn? Raccoons, skunks, turkeys and moles often dig for grubs. Cut a square foot of sod and count before treating.
Do grubs come back every year? They can. Beetles lay eggs each summer, so a treated lawn can be reinfested. Sample before treating instead of treating by default.