You’re enjoying your lawn one day when you spot something unusual: patchy brown spots, grass that lifts easily as if it were low-quality carpet, and perhaps even raccoons or birds scratching away at the ground. It’s likely that you’ve got an invasion of lawn grubs.
While a
healthy lawn
Can handle a small number of these pests, but a complete grub infestation is a challenge that demands attention.
What exactly are grubs, and how can they be detrimental to your lawn? To shed some light on this matter (intended as a play on words), Family Handyman sought insight from Valerie Smith, who is both a specialist in lawn care and a Content Strategist at
Sod Solutions
We’ll go over all the essentials to help elevate your skills.
turf
back: how to identify the initial warning indicators and ways to eliminate them before your lawn becomes an all-you-can-eat feast.
What Are Grubs?
Lawn grubs, also known as grub worms, are the pale, C-shaped offspring of various beetle species residing just below your grassy area. These pests feature six legs near their head end, possess dark-colored heads, and grow anywhere from a quarter-inch to two inches in length.
Beetles’ larvae, known as grubs, consume grass roots, which hinders the plants from absorbing water and essential nutrients. If not controlled, these pests can transform healthy lawns into dry, sparse patches of land.
Kinds of GrubSpecies Found in North American Region
The primary varieties encountered in the U.S. include billbug larvae and scarab beetle larvae, often referred to as white grubs.
Billbug grubs
Billbugs have grub-like larvae that are legless, appearing either tan or cream-colored, and form into a C-shape. These creatures can be identified by their reddish-brown or dark brown heads. What sets them apart from typical grubs is that they consume grass stems internally prior to burrowing underground to feast on roots, complicating early identification. The harm caused by these pests frequently gets misinterpreted as due to dehydration or fungus problems.
According to the
Entomological Society of America
, the most prevalent billbug species encountered in lawns throughout the U.S. include:
- The hunting billbug (Sphenophorus venatus vestitus) frequently causes issues in the southern states and the transitional zones.
- The bluegrass billbug (Sphenophorus parvulus) is commonly found throughout the northern United States and southern Canada, particularly prevalent in areas with cool-season grasses.
- Denver billbug (Sphenophorus cicatristriatus): Targets lawns in the Rocky Mountains and northern Great Plains.
- Phoenix billbug (Sphenophorus phoeniciensis): Attacks bermudagrass and zoysiagrass in the Southwest.
- Lesser billbug and Unequal billbug: Found in more localized regions but still damaging when populations surge.
Scarab beetle grubs (white grubs)
These are the typical white, C-shaped larvae commonly known to homeowners. Despite having over 1,300 scarab beetle species across the U.S., just a few cause issues for lawns. Below are the common culprits:
-
Japanese beetle
(
Popillia japonica
): invasive and widespread -
June beetles
/
May beetles
(
Phyllophaga spp
.): A substantial number of indigenous species -
Masked chafer
(
Cyclocephala borealis
) -
Argentinian scarab
(
Cyclocephala signaticollis
): invasive -
African black beetle
(
Heteronychus arator
): invasive -
European chafer
(
Amphimallon majale
): invasive -
Asiatic garden beetle
(
Maladera castanea
) -
Oriental beetle
(
Anomala orientalis
)
The Life Cycle of Lawn Grubs
When lawn grubs appear, they do so without fanfare. There isn’t any striking alert; instead, you might notice only brown spots, sparse grass, or sections of your lawn that roll back easily, akin to lifting a carpet. The destruction has been happening beneath the surface long before these signs become evident.
To manage them effectively, it helps to understand how they live, grow, and feed. Most lawn-damaging grubs — whether they’re the C-shaped larvae of scarab beetles or the legless larvae of billbugs — go through four life stages. Knowing this is key to determining when and
How to Effectively Treat Lawn Grub Infestations
.
Egg stage
Grub season begins in summer when adult beetles and billbugs lay their eggs in the soil. Timing depends on the species and location — billbugs start earlier (as early as May), while scarab beetles typically lay eggs from June through August. Moist, healthy turf is ideal for egg-laying, which is why well-kept lawns often become targets.
Within
10 to 14 days
, the eggs hatch — and that’s when the true problems begin.
Larval stage
This represents the phase with the highest level of destruction. After hatching from their eggs, the grubs start consuming the roots of the turf grass.
-
White grubs
(from beetles) go through three larval or instar stages, growing larger with each molt. They’re most active near the surface in late summer to early fall. -
Billbug larvae
begin by feeding inside grass stems, working their way down to the crown and root zone. These grubs don’t have legs and tend to damage new lawns, especially those recently sodded.
Because young grubs are smaller and closer to the surface, this stage is the best time to treat with insecticides or biological options. Waiting too long allows them to burrow deeper and cause more damage.
Pupal stage
During autumn, as the temperature drops, fully grown grubs transition into a non-feeding state known as the pupal stage. They create protective cocoons within the ground where they will remain dormant for several weeks or even months before emerging as full-grown adult beetles.
Currently, the treatments are not effective because the grubs have entered their dormant stage and have stopped eating, making them unreachable by insecticides.
Adult stage
When spring arrives, the cycle starts again. Adult beetles and billbugs emerge from the soil to feed, mate, and lay new eggs.
How Do I Know if My Lawn Has Grubs?
The harm caused by grubs might not be immediately apparent—but once you recognize the signs, your lawn will indicate when something’s amiss.
“As long as they’re provided with the proper conditions and sufficient time, grub worms can entirely devastate a whole lawn,” explains Valerie Smith from Sod Solutions, a company supplying grass for both business and home landscapes. Identifying the issue early is crucial—before the harm spreads extensively or cannot be fixed.”
Here are the early
signs of grubs in grass
:
-
Areas with brown spots that seem soft when stepped on:
Damage from grubs usually appears as uneven brown spots that do not recover with irrigation. Walking over these sections can feel soft and springy because of lost roots—similar to pressing down on a wet sponge. -
The tug test:
A classic sign of severe infestation is when sod can be rolled back easily, revealing loose, rootless soil and perhaps even a writhing cluster of grubs just below the surface. -
Wildlife visitors:
If you suddenly notice
holes in your lawn
from birds, skunks or
Raccoons rummaging through your grass area
This might indicate that a grub feast is happening. These hunters are fond of snacking on grubs and will rip apart lawns to reach them.
How Can You Evaluate the Severity of Grub Problems?
One sure way to tell if you have grubs is to actually see them in your soil. To confirm an infestation, perform the square-foot test:
- Slice out a section of sod measuring one foot squared on all but one side.
- Remove the covering and examine the uppermost layers of dirt.
- Count the grubs.
- Duplicate this throughout various areas of your yard.
When Is the Optimal Time for Treating Grubs?
-
Late spring to early summer is when the preventive treatments are most effective, just before eggs hatch.
The most effective preventive treatments occur from late spring through early summer, right before the eggs hatch.
-
The optimal time for therapeutic treatments is late summer since the larvae are vigorously feeding close to the soil’s surface during this period.
The most effective curative treatments are applied in late summer, when the larvae are vigorously eating close to the ground’s surface.
When Should I Treat Lawn Grubs?
A lawn doesn’t always require treatment just because it has grubs. Spotting 0–5 grubs per square foot generally isn’t cause for concern. However, if you count more than five or notice that your lawn isn’t particularly robust, prompt action should be taken as recommended by Smith.
Ways to Address Lawn Grub Infestations
The most effective lawn grub treatments rely on when you detect the problem and the extent of the damage that has occurred.
Chemical Methods for Managing Grubs
Sod Solutions suggests using Dylox 6.2 Granular White Grub Insecticide, which should be applied with a
broadcast spreader
And ensure it’s watered within 24 hours. Nonetheless, this product is harmful to wildlife and should not be allowed into storm drains or drainage ditches.
Grub-killing products
can prove very effective — provided the timing is right.
Implement preventive measures such as using chlorantraniliprole in late spring through early summer before the eggs hatch. This treatment is deemed low-risk for both pollinators and pets when applied according to instructions, which makes it a more secure option for households with children or animals frequenting the lawn.
For therapeutic measures, apply trichlorfon or carbaryl during late summer when grubs are close to the soil’s surface and eating vigorously. Although these substances work quickly, they come with significant toxicity concerns and can endanger bees, aquatic organisms, and helpful bugs. Use them carefully, keep away from water sources, and restrict walking on the grass until it dries completely.
Always follow label instructions, water the treatment in thoroughly and avoid mowing immediately afterward.
Natural and Organic Solutions for Controlling Grubs
For eco-conscious homeowners, beneficial
nematodes
and
milky spore
offer nonchemical options.
Nematodes are tiny worms that prey on and eliminate grubs. Milky spore refers to a naturally occurring ‘infection’ that targets grubs without causing harm to other vegetation or animals. This method requires spreading the spores multiple times across a span of two years for effectiveness.
protect your lawn
for ten years or longer.
Both methods require consistency and may take longer to show results, but they’re safe for pets, pollinators and the environment.
Environmental Factors to Consider When Selecting Treatments
Chemical pesticides may affect helpful insects, groundwater, and surrounding wildlife. Whenever feasible, opt for targeted treatments and steer clear of broad-spectrum insecticides that damage pollinators and other organisms.
overlooked creatures in your garden
If you reside close to water bodies, opt for natural solutions or seek advice from an expert for environmentally friendly choices.
Professional Treatments vs. DIY
For smaller lawns and minor infestations, DIY methods often suffice; however, extensive or persistent grub issues might be better handled by professional lawn care services. Experts can pinpoint the specific species, administer treatments more efficiently, and also detect any hidden issues.
soil health
concerns leading to the issue.
What Are Some Methods to Stop Lawn Grubs from Returning?
While grubs might be hidden from view, they should not be forgotten. A well-maintained lawn serves as the best protection against grubs and beetles.
-
Fertilize your lawn
one or two times per year and
remove built-up thatch
. -
Create a bird-friendly habitat by placing
birdhouses
and add bird baths to your yard to
attract insect-eating birds
Similar to robins, wrens, and jays, they will consume the grubs as well as the beetles. -
You might want to think about considering this option.
organic lawn fertilizer
, particularly if you’ve added beneficial nematodes. Certain chemical fertilizers can be harmful to these nematodes.
FAQs About Lawn Grubs
What leads to the presence of grubs in your lawn?
Beetles lay their eggs in your lawn’s soil during midsummer, resulting in grubs. The presence of moist earth, accumulated thatch, and dense grass tends to attract these egg-laying insects.
Is grub damage reversible?
Certainly. After treating the grubs, reseed or lay new sod over the impacted sections. If properly watered and cared for, the grass should regenerate, particularly if this is done during early fall or late spring.
Can grubs be detrimental to pets?
The grubs aren’t poisonous, but the pesticides used against them can be dangerous. Make sure to adhere strictly to the label directions and avoid letting your pets access the treated zones until the specified period has passed.
Do white grubs return each year?
Adult beetles frequently go back to suitable lawns for laying their eggs. Maintaining and regularly inspecting your lawn can decrease the likelihood of reinfection.
About the Expert
Valerie Smith
serves as a lawn care specialist for
Sod Solutions
With over 25 years of expertise in the turfgrass sector, this company leverages its extensive knowledge of grass health and sustainable lawns. Valerie assists both home owners and specialists in making well-informed choices regarding lawn upkeep, routine maintenance, and insect management.
Sources
-
Journal of Integrated Pest Management, Vol. 7, No. 1, January 2016, Page 6
Biology and Management of Billbugs (Coleoptera: Curculionidae) in Lawn Grass
-
Envu | Cutting-Edge Environmental Innovations
: “Billbug”
-
Envu | Cutting-Edge Environmental Innovations
: “White grub”
-
Purdue University Publications
: “Turfgrass Insects”
-
Clemson University’s Home & Garden Information Center
Management of White Grubs in Turfgrass
-
Colorado State University Extension
Controlling Billbugs and White Grubs in Residential Turfgrass
-
Michigan State University Extension
How to Select and Apply Grub Control Products for Your Lawn
-
National Pesticide Information Center
: “Carbaryl Fact Sheet”
-
National Pesticide Information Center
: “Chlorantraniliprole Fact Sheet”
-
Missouri Botanical Garden
: “Grubs in Lawn”
-
University of Georgia Extension
: “White Grubs”
-
Scotts
How to Manage Lawn Grubs
