Lawn grubs, sometimes known as white grubs, are white, C-shaped beetle larvae about a half-inch long. A grub could be the larvae of the masked or European chafer, a Japanese beetle, or another beetle species. Lawn grubs have soft bodies and legs that are close to the head.
What are lawn grubs?
Lawn grubs are the wriggly, worm-like larvae of several beetles that hatch in the spring and summer, such as Japanese Beetles and June Bugs. These bugs are about an inch long and coil up into a C shape when disturbed. They dig into your lawn and munch on the grass. They’re fine in small quantities, but if big populations go unchecked, they can cause considerable damage.
How to tell if your lawn has lawn grubs
Grub damage might manifest itself in two ways. Small irregular portions of a lawn will initially appear brown, dry, and withered. Raccoons and crows also cause damage by tearing through the lawn to feast on grubs. During a strong outbreak, both types of harm might be considerable.
Grubs may have eaten the root system if you can pull the sod away from the ground. Examine the soil for signs of their presence. More than ten grubs per square foot is a warning sign.
The sight of grubs on your lawn could indicate that beetles are laying eggs there. Tan-colored chafer beetles are active shortly after sundown, while Japanese beetles can be spotted flying during the day, for example, eating on ornamentals.
The only way to be certain that you have grubs is to patrol your lawn for them.
- Make a one-foot cut in your grass where you suspect grub activity with a shovel or a lawn edger.
- Remove a one-square-foot portion of grass and dirt from the cut. If there is considerable grub damage, the grass should easily peel up.
- Sift over the earth, counting how many grubs you find. You have a major infestation if you find 10 or more grubs per square foot. Finding a few grubs is usual and does not indicate a problem.
- Replace the grass you’ve cut as soon as possible to avoid causing damage to the lawn.
Depending on the size of your lawn, you may wish to scout for grubs in different places. Just because there are a lot of grubs, or not a lot of grubs, in one square foot does not suggest that the entire lawn has a grub infestation. You might concentrate your scouting efforts on sections of the grass that are showing signs of grub feeding.
Take notes while you scout for grubs in your lawn, so you remember which places have high counts and which don’t. This is important f you decide to treat the lawn.
How bad are grubs on the lawn?
The larval or immature stage of various beetles and chafers, Grubs can harm your lawn by feeding on its roots. Healthier grasses can withstand more grub feeding, although all grass can withstand some grub feeding.
A grub infestation will result in spots of thinning turf that will eventually grow in size. Grub-damaged grass frequently pulls out readily at the roots.
Homeowners frequently tell us they feel they have grubs because animals such as moles, skunks, crows, and raccoons are digging in their grass.
However, this isn’t always a good indicator because grub infestations aren’t usually accompanied by animal damage, and animal damage isn’t necessarily the outcome of a grub infestation. These critters eat other insects in the grass, such as earthworms, good for the lawn’s health.
All of this being said, if you have grubs and animals are digging for them in your grass, it can be harmful to the health of your turf and the beauty of your yard.
Is it necessary to treat grubs?
If you have a high concentration of grubs — 10 or more grubs per square foot – treatment may be required to keep your grass healthy. However, if you have a lower grub count but aren’t seeing positive results in your grass, it’s a sign that you should reconsider your lawn care practices in general.
Some of the best practices that we advocate are as follows:
- Conducting soil tests every 2-3 years and adhering to fertilizer and amendment recommendations.
- Keeping grass trimmed high — at least 2 inches, ideally 3 inches or more – implies your grass will have a stronger, healthier root system that can withstand more subsurface insect feeding.
- Spring or fall overseeding of barren or sparse areas (preferred).
Types of lawn grub control
To control garden pests, an integrated pest management (IPM) program, also known as integrated pest control (IPC), employs a variety of approaches. It includes preventative measures, regularly monitoring, environmentally acceptable pest control technologies, and the proper use of pesticides.
An aggressive IPM program is the most effective way to deal with grass pests. Scouting regularly is the best defense, especially late in the summer when grub damage is at its worst.
If you have cut into the soil and established an outbreak has occurred, you could use an insecticide like Dylox. (Insecticides such as Merit help in preventing grubs while they are in the egg stage.) It’s also a good idea to wait until a fresh lawn has grown before adding grub killer chemicals.
Insecticides are hazardous and should only be applied by a qualified pesticide applicator. Insecticides also harm pollinators like bees, who feed on flowering clover weeds on lawns. Protect pollinators by applying insecticide when weeds are not in bloom or by mowing down blooms before application to prevent bees from ingesting the toxins.
The two most frequently asked about natural goods are milky spores and nematodes.
Milky spore is a bacteria that is excellent at controlling Japanese beetle larvae in spring soils that are warm enough.
While a study on milky spores in our location has not been conducted recently, the most recent research findings indicate that spring soils in Northern New England are too cold for the milky spore to succeed.
There is anecdotal evidence that it has at least some efficacy in warmer microclimates in southern New Hampshire. If you are: Milky spore may be worth a go if you are:
- Confirm that the grubs in your lawn are Japanese beetle larvae (identifying grub species requires a hand-lens because the distinctions are minute)
- Live in a warmer environment in southern New Hampshire
Keep in mind that it will take several years for the milky spore to produce good results.
Nematodes are microscopic worms that can be quite effective at reducing grubs in household lawns. To use nematodes successfully for grub control, keep the following principles in mind:
- The lawn must be well watered, and the soil must not dry out while the worms establish.
- The nematodes must be viable (alive) when administered. It is critical to buy nematodes from a reliable supplier and to apply them as soon as possible.
- You have to apply the right species of nematode at the appropriate time of year.
- Nematodes are light sensitive and can be killed in a minute if exposed to direct sunlight — it’s best to apply them on a cloudy day or early in the morning.
- Some nematode species exclusively control specific species of grubs. Thus determining what species of grubs you have is important, just as it is with milky spore. Nematodes must also be used while the grubs they control are active in the soil.
- If nematodes are used to treat an infestation, they may need to be treated every two weeks until the infestation is gone. Nematodes should be applied twice or three times per season for individuals who use them as a preventative measure.
Nematodes can be an excellent natural choice for eradicating grubs for home gardeners who do their homework and follow instructions attentively.
Beetles lay their eggs in irrigated, damp soil. Avoiding watering your grass during summer’s dry periods is a natural preventative measure. The lawn may turn brown and die, but a grub infestation is unlikely.
What chemical treatments can I use to keep grubs at bay on my lawn?
You have a few options if you have a serious grub infestation and wish to use a chemical treatment to control the grubs.
From late April to early June, you can effectively control all species of white grubs in New Hampshire by using a product containing the active ingredient, chlorantraniliprole. This chemical is also effective against caterpillars such as webworms and armyworms.
This treatment is most effective when the grub is actively feeding, so it should be used 2 to 3 months before severe grub feeding on June to August.
This chemical can be found in two commonly used products: GrubEx® and Roundup® For Lawns Bug Destroyer. The US EPA classifies this compound as a low-risk pesticide because of its minimal toxicity to bees and other beneficial insects.
In the neonicotinoid class of insecticides, there are various alternative preventative products. Imidacloprid, thiamethoxam, and clothianidin are a few examples. Neonicotinoids are systemic and are absorbed by grass, killing grubs not on touch but when they feed on the roots of treated plants.
To regulate the grubs while active, these compounds and the products they’re in all require slightly different application times. These compounds are most effective from mid-June to early August.
Merit®, Meridian®, and Arena® are examples of neonicotinoid-based grub control products. There are also several prophylactic medicines available, including a neonicotinoid and a pyrethroid that eliminate grubs and caterpillars, billbugs, and certain other lawn insect pests.
Some treatments certified for grub control solely contain a pyrethroid, such as those containing the active component Gamma-Cyhalothrin, which is typically found in Spectracide® Triazicide® Insect Killer For Lawns.
According to Michigan State University research, products containing solely lambda-cyhalothrin, gamma-cyhalothrin, bifenthrin, deltamethrin, cyfluthrin, or permethrin are ineffective for grub control.
Only curative products can be used to effectively manage grub populations at this time of year (late summer and fall). Ingredients like carbaryl, trichlorfon, and zeta-cypermethrin are curative and work when they come into touch with grubs. Sevin® and Dylox® are two examples of products that contain these compounds.
These chemicals can be useful, but they are broad-spectrum and have a low residue, killing beneficial insects and grass pests like grubs on contact. Their effectiveness is also highly variable, with wide-ranging results with as little as 20% to 25% control.
These products should be thoroughly watered soon after application. The later in the season these treatments are applied, the further below the soil the chemical must go to reach the grubs.
Most of the time, whether it’s early spring or late fall, it’s wiser to just wait until the next reasonable opportunity to use a preventative treatment that produces better benefits and is more targeted. UMass Extension has more information on current pesticide techniques for white grubs.
How can I keep grubs at bay while also protecting bees and other pollinators?
Before spraying any insecticides, the grass should be mowed to prevent weeds from blossoming in the lawn while the substance is being administered.
Keep an eye out for drift. If you spray an area of your lawn while it is windy, the product may fly onto surrounding floral plants. Similarly, if you’re using a granular solution with a spreader, be sure you only apply it to grass areas that have been mowed and have a grub infestation.
If only a portion of your lawn is infested with grubs, there’s no reason to apply any of these products to the entire lawn. Only use pesticides to control grubs if essential, and always read and follow all label instructions.
Repairing lawn grub damage
Because the grubs eat on the roots, the grass must be replanted. Simply treat the area as you would any other bare patch repair, and make sure to keep the seed moist while it germinates. Here are the fundamental steps:
- Rake the lawn and remove any loose or dead patches.
- Aerate the lawn.
- Reseed the lawn.
- Water seeds thoroughly to help them form roots.
- Keep an eye out for flipped-over bits of fresh lawn; just flip them back over.
What do grubs turn into?
Adult scarab beetles emerge from the dirt to mate and lay eggs after grubs develop. Adult beetles do not cause significant damage to lawns. When the adults lay their eggs, which hatch into these troublesome, ravenous tiny grubs, they cause significant damage to your lawn, ornamental grasses, and flowers. Scarab beetles, which have strong, metallic bodies, emerge early to midsummer to mate and produce eggs.
Dung beetles, often known as scarab beetles, are not harmful to your lawn because they feed on dung and are good for the soil. However, grubs can transform into a variety of bothersome scarab beetles, including:
- Asiatic garden beetles
- Green June beetles (June bugs)
- Black turfgrass ataenius
- Northern masked chafers
- Japanese beetles
- European chafers
- Oriental beetles
Billbugs are not scarab beetles, although grubs can develop into these nasty pests. Except for Florida, billbugs are common throughout the majority of the United States. Adult billbugs are either creamy or brown in color but not metallic. They chew holes in the grass to lay their eggs. Because they feed on the grassroots, both adults and larvae are equally damaging.
Tips for prevention and maintenance
- Using a prophylactic grub control solution in the spring or early summer will provide far better grub control than waiting until the damage has occurred.
- Apply Scotts® GrubEx®1 using a spreader. Make careful you follow the application instructions.
- Water shortly after applying the product to activate it.
- A stressed, underfed lawn will reveal grub damage faster and with fewer grubs per square foot than a properly fed, well-maintained grass.
- A well-maintained lawn can withstand more grubs per square foot than a stressed lawn.
Last update on 2022-06-30 / Affiliate links / Images from Amazon Product Advertising API