Some insects are extremely beneficial to your lawn. Pollinators help plants reproduce, predators get rid of unwanted pests and saprophytes help break down dead plant matter into nutrients in the soil. Some insects, however, do nothing but damage to grass. White grubs, in particular, are a bane to many homeowners who want a lush, green lawn.
These grubs aren’t their own insect species, but are instead the larval stage of several different kinds of beetle. They live beneath the surface of the soil, feeding on roots until the grass above withers and dies. Because they live underground and return every year, they can be difficult to kill. However, by using the right method at the right time, you can kill the grubs before they do significant damage, or even prevent them from hatching in the first place.
In this article:
- Identifying Grubs
- Preventing Lawn Grubs
- Using Nematodes
- Applying Insecticide
- Top Pick: TruGreen
- Frequently Asked Questions
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If you’ve got a lawn grub infestation that’s not responding to DIY pest control methods, consider hiring a professional lawn care and pest control company. The reviews team recommends TruGreen, a nationwide company with many years in the business of caring for lawns, which includes eliminating common pests.
When people refer to “lawn grubs,” they’re usually talking about white grubs, which are the larval stage of many different types of beetle. These grubs have soft, white bodies that tend to curl into a C-shape when disturbed. They may be anywhere from ⅜-inch to 2 inches long, depending on the species of beetle. Here are some of the types of beetle that are most likely to introduce grubs into your lawn:
- Japanese beetle: This invasive species is most common on the east coast and is notorious for eating nearly any kind of plant it comes into contact with.
- Masked chafer: Several species of masked chafer act as pests that damage crops and lawns across the country.
- European chafer: Also known as June bugs, these beetles tend to infest cool-season grasses.
Not only are these adult beetles destructive, their larvae can do plenty of damage while still living beneath the ground. These grubs feast on grass roots, creating widening, irregular brown patches of dead turf. In addition to directly damaging the grass, lawn grubs also attract animals like raccoons, moles and birds, which love to snack on the bugs. These animals — particularly moles — can destroy your lawn while digging for grubs to eat.
If you suspect your lawn may be harboring a grub infestation, perform an inspection. Grub-related dead patches tend to show up in the fall, so if you saw a large number of adult beetles during the spring or early summer, give your soil a check.
To do this, pull up the turf around damaged areas and look through the top 2 inches or so of soil. If there aren’t any damaged places yet, randomly spot-check your yard. If you find more than about six to 10 grubs per square foot, you should consider treating your lawn.
Preventing Lawn Grubs
If at all possible, you want to prevent a white grub infestation in the first place. Although none of these methods is foolproof, keeping up with regular lawn maintenance can go a long way toward preventing common problems including lawn grubs.
Grow Grub-Resistant Grass
Certain species of grass are more likely to attract grubs than others. Kentucky bluegrass is an extremely popular cool-season grass, but it’s a favorite meal for beetle grubs. Consider switching to a hardier species like tall fescue.
Eliminate Adult Beetles
Keep an eye out for beetles during the spring and summer. Japanese beetles will fly around during the day, and masked chafer beetles will come out at sundown. If you start seeing adult insects, it’s a fairly certain sign that they’re laying eggs in your yard. Use a pesticide designed to eliminate beetles, such as one that contains pyrethroid, every three to four weeks during peak season.
Water Irregularly but Deeply
High soil moisture during the summer can attract adult beetles to a lawn to lay their eggs. You can’t do much about rainfall patterns, but you can avoid overwatering your lawn. Instead of watering by a set schedule, check the dampness of your soil and only irrigate when it’s dry. Then, water to a depth of 6 to 8 inches, which will encourage grass roots to grow deeper and stronger in search of water.
Raise Your Mower Blades
Particularly in the summer, let your grass grow a little longer than you normally would — at least 3 to 3.5 inches. Not only will this help keep weeds from growing, but it will also act as a safeguard against grub damage. Taller grass has a higher amount of root mass and can better withstand any grub activity.
Use Preventive Insecticide
If you aren’t able to kill off the adult beetles before they lay eggs, you can purchase pesticide that will kill the eggs themselves before they hatch. Insecticides that contain imidacloprid are good preventive products.
Fertilize in the Fall
In addition to grub prevention, it’s also a good idea to strengthen your grass. A healthy, well-fertilized lawn will be better able to prevent or survive a grub infestation. Cool-season grasses, like those grown most places in the United States, need feeding in the fall to bulk up before going dormant in the winter.
If you hate the damage that grubs do to your lawn but you aren’t sold on chemical insecticides, you can try introducing organisms to your lawn that will kill the grubs without harming any plants or wildlife.
Nematodes are microscopic worms, and a species of nematode called Heterorhabditis bacteriophora acts as a parasite to white grubs. Once it has infected an insect, the nematode releases a bacterium that kills the grub within 48 hours.
You can purchase these nematodes online or at many home and garden stores. The packaging will contain directions on how to apply them to your lawn, but usually you’ll add them to water and spray the mixture over your grass. Do this in late summer or early fall, and reapply two weeks later for the best results. Bright sunlight can kill these worms, so apply them in overcast or rainy weather. Nematodes work best for pest control in moist soil, so keep up with your watering.
Although the grubs will die soon after the nematodes infect them, this solution can still take a while to work its way through your lawn. Additionally, using nematodes represents a time investment when it comes to applying them and monitoring your lawn conditions, so it’s not a quick fix.
Nematodes will, however, help balance the microorganisms in the soil and process nutrients into forms plants can absorb, so they may be worth your time.
Insecticides are highly effective against lawn grubs. They will, however, kill off most beneficial insects in your lawn, in addition to soaking the soil with toxic chemicals.
When the infestation is severe enough, though, this may be your best choice to save your lawn. When applying insecticide, you’ll need to decide between a preventive and curative approach.
Curative treatment takes place after the grubs have hatched, which is usually in late summer or early fall. Lawn grubs are easiest to kill when they’re young, so early to mid-August is usually the best time to apply a curative insecticide.
These products will only remain effective in the soil for two to three weeks, so proper timing is essential. Perform inspections around areas that get a lot of sun to see if you need curative treatment.
Preventive treatment, on the other hand, doesn’t rely on such precise timing and inspection. Preventive products remain active in the soil for up to two to three months, so you can apply them in late spring to take care of any eggs or newly hatched grubs.
The drawback here is that you may be treating a problem that isn’t actually coming, and you’ll find you’ve drenched your soil with long-acting chemicals for nothing. Preventive approaches work best when you can pinpoint spots of previous infestation.
Going the Green Route — Organic Only
Using predatory insects like beneficial nematodes is one way of killing grubs organically, but there are others. One risky approach is letting your lawn dry out to deprive the eggs of moisture. Cool-season grasses go dormant in the summer when eggs are hatching, so you still may be able to revive the grass in the fall, but you do risk damaging your lawn.
Neem oil is a vegetable oil made from pressed seeds of an Indian evergreen tree. Although it’s toxic if swallowed, it’s used in cosmetics in some parts of the world, but in the US, it’s primarily used as an organic pesticide.
It won’t harm pets, earthworms or most beneficial insects, and it’s biodegradable, so some homeowners prefer it to synthetic pesticides. It can also kill certain types of lawn fungus.
Another organic curative pesticide, milky spore, is a bacterium that’s lethal to Japanese beetles. It’s commonly sold as a powder that both grubs and adult beetles will ingest. The insects will usually die off between one and three weeks after consuming milky spore. However, it is only effective against Japanese beetles, not chafer beetles, so be sure you know which species you’re dealing with. Milky spore is also best at controlling grub populations, not eliminating them completely, and it can take several growing seasons to become widely effective.
Going with the Pros
If you’ve tried some of the above methods and found them ineffective, or if you’re dealing with a severe infestation, there’s no shame in calling in the professionals.
A lawn care company will be able to analyze the problem and provide a comprehensive solution, and its technicians will have the right training and equipment to implement it.
TruGreen gets the reviews team’s recommendation as the preferred nationwide lawn care company.
Top Pick: TruGreen
TruGreen offers a specific grub control and prevention service. A technician will monitor your lawn for adult beetle activity in the spring to help determine whether treatment is needed. If so, TruGreen will apply a preventive product that will kill eggs and newly hatched grubs come summer.
TruGreen also offers a number of comprehensive, annual lawn care packages in all states except Alaska and Hawaii to repair any grub-related damage and boost the health of your lawn to make it a less friendly environment for grubs.
To learn more about grub control or receive a free estimate for treatment of your lawn, fill out this simple form or call 888-535-3193. Grub infestations are easier to control if you get started early, so explore your options as soon as possible.
Frequently Asked Questions
When should I treat my lawn for grubs?
The answer depends on which type of treatment you decide to use.
Preventive treatments kill beetle eggs and newly hatched grubs, so they should be used in the early-to-mid-summer.
Curative treatments kill live grubs, so they should be used in the late summer or early fall, usually in August, before the grubs grow too large.
Finally, if you’d prefer to eliminate the beetles themselves before they can lay eggs, use pesticides when they’re active in the spring.
How do I know if there are grubs in my lawn?
Telling the difference between grub activity and other kinds of lawn damage can be tricky, but it should be possible with some close inspection.
Here are some signs that grubs are causing the problem:
- Any brown, dead patches are irregular in shape: Fungus and animal urine can also cause yellow or brown patches in grass, but they tend to be circular in shape. Grub damage, on the other hand, expands irregularly through a lawn.
- The grass comes up easily when pulled: Grass that has been eaten by grubs is truly dead, rather than sick or dormant, and thus will pull up by hand without much effort. There won’t be much in the way of roots, either.
- The lawn feels spongy when walked on: Grubs munching through grass roots can alter the structure of the soil, so your grass may feel spongy even though it’s well-watered.
There are more than 10 grubs per square foot of soil: A few grubs are normal and won’t cause much damage, but a visual inspection can tell you how bad the problem is.
If you see fewer than five grubs in the top 2-4 inches of a square foot of soil, you don’t need to treat.
Six to nine grubs per square foot probably doesn’t require treatment unless predators are getting into your yard.
But 10 or more grubs requires some kind of intervention.