Grub Control: How to Find, Count and Treat White Grubs in Your Lawn

Brown patches are spreading across your lawn, watering does not bring them back, and something has been digging holes overnight. White grubs are a common cause. They are also one of the most over-treated lawn pests, because plenty of lawns get a grub product every year whether they need one or not. This guide shows you how to confirm grubs, count them, and time a treatment so it works the first time.

How to identify white grubs

White grubs are the larvae of several beetles, including the Japanese beetle, masked chafers, the European chafer, the Oriental beetle and May or June beetles. They all look much alike:

• Soft, dirty white body with a brown head.
• Six small legs near the head. (Green June beetle grubs are the exception; their legs are poorly developed.)
• Lying curled in a C shape when you lift the sod.
• About 1 inch long when full grown, for common species like Japanese beetle and northern masked chafer grubs.

Telling species apart takes a hand lens and a look at the spine pattern under the last segment. Your county extension office can help, and it matters because thresholds and timing differ by species.

Not every brown patch is grubs. Here is how the usual suspects compare.

If you see raised tunnels or round mounds of soil instead, read about moles. Moles do eat grubs, but they also eat earthworms, so a mole problem alone does not prove you have grubs.

Signs of grub damage

• Patches that wilt and stay wilted even after you water, and turf that feels spongy underfoot.
• Sod that rolls back with almost no effort, because the roots are gone.
• Damage that shows up in late summer or fall, or again in spring as grass greens up. In Pennsylvania, dead patches are most visible in April to May and September to October.
• Animals digging. Skunks, raccoons and birds tear up turf to get at grubs, and that digging is often the first thing homeowners notice.

The peel-back test: how to check for grubs

Do this before you buy anything.

1. Pick several spots, including the edge of a brown patch where it meets green grass.
2. Cut three sides of a one-foot square with a flat spade, 2 to 4 inches deep.
3. Fold the sod back and break apart the soil and thatch. Grubs may be just under the roots.
4. Count the grubs in each square, then average the count across your spots.
5. Press the sod back down and water it so it does not dry out.

The best time to sample is August through early September, when grubs are small and close to the surface. A quick shortcut is the tug test: grab a handful of grass at the edge of a patch and pull. If it lifts like carpet, dig there.

How many grubs is too many?

A few scattered grubs are normal. Healthy, well-watered turf can handle more feeding than stressed turf. Use these numbers from extension programs as a starting point.

Penn State uses 5 to 10 grubs per square foot as a general curative threshold and stresses that every lawn has to be judged on its own.

Why grubs show up

Adult beetles lay eggs in the soil in summer. For the common species, eggs hatch in about 10 days to three weeks, and the young grubs feed on roots near the surface through late summer and fall. When the soil cools, they move several inches deeper for the winter, then come back up in spring to feed again before they pupate. May and June beetles are the slow exception, with a three-year life cycle.

Eggs need moist soil to survive. That is why heavily watered lawns can attract egg-laying beetles in midsummer. Thick thatch also draws egg-laying and can keep some insecticides from reaching the soil.

How to get rid of grubs, step by step

This follows the integrated pest management order: confirm the problem, fix conditions, then treat only where needed.

1. Sample first. Use the peel-back test. If your counts are below threshold, skip the insecticide and focus on lawn health.
2. Water and feed the lawn properly. Turf with deep roots tolerates grub feeding and recovers faster. Avoid heavy watering in July if you have had grubs before.
3. Consider a dry spell. Letting the lawn go dry in July and early August can kill eggs in the soil, but the grass will turn brown until you water again.
4. Dethatch or aerate if thatch is over half an inch.
5. Treat only the areas that need it. If grubs are concentrated in a few zones, a curative spot treatment uses less product.
6. Reseed bare areas once the grubs are under control.

Preventive vs curative products

Grub insecticides come in two groups, and a product applied at the wrong time can do almost nothing.

A few timing details from Ohio State: imidacloprid and thiamethoxam stay active for up to about 8 weeks and should not go down before mid-June, while clothianidin and chlorantraniliprole last up to about 12 weeks and can go down as early as late May. Pyrethroids by themselves do not control grubs, so a combination product only works against grubs because of its other ingredient.

Spring applications are generally the weakest choice. Grubs are large, close to pupating and harder to kill, and short-lived products give no protection against the eggs laid later that summer.

Water it in. Almost every grub product needs about 1/4 to 1/2 inch of irrigation or rain soon after you apply it to move the active ingredient down to the roots. If the soil is dry before a curative treatment, water first. Skip this step and control is poor.

Neonicotinoids (imidacloprid, clothianidin, thiamethoxam and dinotefuran) can harm bees and other pollinators. Read and follow the label, and see using pesticides safely before you buy. Some lawn products are restricted to licensed applicators in certain states.

Wisconsin notes that most lawns there never need a grub treatment, and Purdue points preventive treatments mainly at turf with a history of grub damage. For most home lawns, sampling plus a curative treatment when needed is usually the better plan.

Beneficial nematodes and other biological options

Insect-parasitic nematodes are microscopic worms that enter grubs and kill them. Heterorhabditis bacteriophora is the species most often sold for lawn grubs. Results are inconsistent, though they are an option if you want to avoid chemical insecticides. To give them a fair chance:

• Keep them refrigerated and use them soon after they arrive. Check the expiration date.
• Apply in early morning or evening, not in hot midday sun.
• Water them in right away, then keep the soil moist for about a week.

Milky spore disease affects only Japanese beetle grubs, can take three to five years to establish, and did not show useful results in recent university trials.

Skunks, raccoons and other animals digging

Animals can shred a lawn hunting grubs, sometimes before the grass itself looks damaged. Controlling the grubs is the main fix, because it removes the food. Trapping the animals takes time, and wildlife trapping rules vary by state, so check with your state wildlife agency first.

If skunks are digging, see our guide to skunks around the house. For raccoons, read raccoon removal and prevention. Do not try to handle or corner either animal.

Lawn care company or DIY?

Grub control is a reasonable DIY job if you sample, pick the right product for the season and water it in. Hiring out makes sense when:

• The lawn is large, or grubs keep coming back year after year.
• You want someone to do the sampling and timing for you.
• You need a product that is restricted to licensed applicators in your state.

What a good visit looks like: the technician cuts sample squares and counts grubs before recommending a product, tells you the active ingredient, and explains why the timing fits your grub species.

Questions to ask:

• Did you find grubs over threshold, or is this a routine preventive application?
• Which active ingredient are you using, and can I see the label?
• Is the applicator certified or licensed? You can check with your state Department of Agriculture.
• Will you water it in, or do I need to?

The EPA notes that routine pesticide applications are usually not advisable unless pests are always present, so if a plan includes a grub product every year, ask whether your lawn needs it. Our guides to choosing a pest control company and pest control costs cover how to compare quotes.

Grub questions

Will killing grubs stop Japanese beetles from eating my plants? That is a separate problem from lawn damage. See Japanese beetle control for how lawn treatments affect adult beetles and how to protect plants.

Can I treat grubs in spring? You can, but it is the least effective time. Mid to late summer is far better.

My lawn has some grubs but no damage. Should I treat? If the count is below threshold, no. Keep the lawn healthy and check again in late summer.