The only way to treat lawn grubs correctly is to confirm they’re present, pick a preventive or curative product for the season, and water it in immediately.
Treating your lawn for grubs without first checking for them is the most common mistake homeowners make. The fix for grub damage depends entirely on whether you’re stopping eggs from hatching or killing grubs that are already feeding on your roots. The steps below walk through confirming the problem, choosing the right chemistry, and applying it so it actually works.
Confirm Grubs Before You Treat
Brown patches in summer can come from drought, disease, or dog urine — not just grubs. University of Illinois Extension advises sampling the lawn rather than treating based on appearance alone.
To check, peel back a section of dead turf and inspect the top few inches of soil. Count the C-shaped white grubs you find. University of Illinois Extension says about 12 grubs per square foot can cause damage worth controlling; Missouri Botanical Garden puts the threshold closer to 10 per square foot. Either way, if you find only a handful, skip the insecticide.
Grubs are often localized. Illinois Extension recommends applying insecticide only in and around the damaged areas, not across the whole yard. Spot treatment also preserves the natural predators that help keep grub populations in check, which the New York Botanical Garden notes as a benefit of avoiding blanket applications.
Preventive vs. Curative: Which Product Do You Need?
Preventive products stop grubs before they hatch and must go down on a schedule; curative products kill grubs already in the soil and work on a shorter window. Using one in place of the other is a waste of money.
- Preventive (April–July): Michigan State Extension says chlorantraniliprole goes down in April or May for fall grub prevention. Clothianidin, thiamethoxam, or imidacloprid are applied in June or July for grubs that damage turf in the fall.
- Curative (late July–August for fall grubs, or spring): Carbaryl (sold as Sevin) and trichlorfon (sold as Dylox) work when grubs are actively feeding. Missouri Botanical Garden says these are typically applied in late July through August.
Michigan State warns against one costly mistake: preventive compounds like imidacloprid should not be used in spring for spring grub control. Save them for June or July. And never rely on products containing only lambda-cyhalothrin, bifenthrin, deltamethrin, cyfluthrin, or permethrin — these pyrethroids do not control grubs effectively, per Michigan State.
The Correct Application Steps
Getting the product down is only half the job. These four steps determine whether the insecticide reaches the grubs or sits useless on the surface.
- Mow first. Michigan State suggests mowing before application to remove weed flowers, which also reduces exposure for bees.
- Apply at the right time. Use a spreader for granules and follow the label rate for your lawn size.
- Water it in. Michigan State says insecticide must be watered in with at least 0.5 inches of irrigation or rain immediately after application. Illinois Extension gives the same instruction. Skip this and the product never reaches the roots where grubs feed.
- Keep people and pets off until dry. Let the grass dry before allowing anyone into the treated area, per Michigan State and Home Depot Canada. Always wear rubber gloves and rubber boots when applying turfgrass insecticides, Michigan State adds.
For an organic alternative, University of New Hampshire Extension notes curative nematodes work, but they may need reapplication every 2 weeks until the infestation subsides.
| Timing | Product Type | Active Ingredients |
|---|---|---|
| April–May | Preventive | Chlorantraniliprole |
| June–July | Preventive | Clothianidin, thiamethoxam, imidacloprid |
| Late July–August | Curative | Carbaryl (Sevin), trichlorfon (Dylox) |
| Spring | Curative | Carbaryl, trichlorfon |
Scotts GrubEx₁ Season Long Grub Killer is a common preventive option found at U.S. retailers. You can compare top-rated options side by side in our roundup of the best grub treatments for lawns.
Helping the Lawn Recover
Watering and fertilizing won’t prevent grub damage, but they will help the turf bounce back faster, says Missouri Botanical Garden. Michigan State adds that proper fertilization aids recovery. Keep watering consistent, but avoid overwatering — Missouri Botanical Garden notes adult beetles actively seek moist, lush lawns for egg-laying, so a soggy yard invites the next generation. Michigan State Extension’s grub control guidance covers the full timing and product details.
References & Sources
- Michigan State University Extension. “How to Choose and When to Apply Grub Control Products for Your Lawn.” Covers preventive vs. curative timing, watering requirements, safety, and ineffective chemistries.
- University of Illinois Extension. “Dealing with Grubs in Lawns.” Explains sampling, damage thresholds, and spot-treatment guidance.
- University of New Hampshire Extension. “How Do I Treat Grubs in My Lawn?” Details nematode application and reapplication intervals.
- Missouri Botanical Garden. Provides damage thresholds and notes on watering, fertilization, and example trade names.