What Are Grubs? A Deep Drive Into These Lawn-Killing Pests
Anyone who’s ever dug a hole in their lawn only to find some fat, C-shaped grub worms likely knows the feeling of horror. They can attract other animals, cause oddly-shaped dead spots in the grass, and turn a gorgeous lawn brown. And worse yet, these little pests are lawn killers, and they won’t go away on their own. But, if you’re like most folks and wondering “what are grubs?,” this guide should help.
What Are Lawn Grubs?
Grubs are the larval stage of adult beetles. Grubs hatch from eggs laid in the soil surface by adult beetles in the early summer to early fall. These pests feed on the root systems of grass, potted plants, ornamental garden plants, and other organic matter. They continue feeding until they’re large enough to pupate into adult beetles.
Commonly known as white grubs, grubs have segmented, worm-like bodies that are usually white or cream in color. White grubs generally have tan or brown heads, and once unearthed, will usually curl up into a C-shape.
The Most Common Types of Lawn Grubs
There are several species of grubs, but in the US, we typically deal with two or three certain species. These species include Japanese beetle grubs, May or June beetle grubs, or European chafer grubs. It’s also worth noting that crane flies can cause a grub problem, but they aren’t actually a beetle species.
Japanese Beetle Grubs
Japanese beetles, and their grubs, are an invasive species that was first discovered in 1916, in Riverton, New Jersey. The adult beetles are trouble in and of themselves, as they feed on plant leaves, trees, shrubs, flowers, and vegetables.
Japanese beetles mate after sunset from Mid-June to late July.
May or June Beetles Grubs
May and June Beetles and their grubs are also an invasive species, but there are over 200 species of these beetles that exist throughout the US. They cause tons of damage to lawns, plants, and gardens.
European Chafer Grubs
European Chafers and their grubs are an invasive species first discovered in Newark, NY in the 1940s. They spread quickly and are one of the most common grubs in the eastern US. These beetles mate from the middle of June until the end of July, waiting until the romantic hours after sunset.
Crane Fly Grubs
Never heard of a crane fly? You might know them by their more common name: daddy long legs. These pests lay eggs that hatch into “leatherjackets,” which aren’t white grubs at all, but a darker grub that will eventually molt into a crane fly. They cause a tremendous amount of damage in their own right, as well.
Grub Life Cycle
Most grub worms have either a 1-year or 3-year life cycle. May or June beetles typically have a three-year cycle, while Japanese beetles have a one-year cycle. Regardless of the length of time, the specific activities that occur are relatively common:
- The life cycle starts when adult beetles lay eggs in the soil during the summer.
- Within a few weeks, grubs hatch from those eggs and begin to feed on grass roots and other organic matter. This lasts for several months or even longer, depending on the species.
- As the grub grows, it will shed its skin. This happens two to three times, depending on the species.
- As the temperature drops, grubs will burrow deep into the soil and spend the winter protected from freezing temperatures.
- As the sun warms the soil in the early spring, grub activity will increase as they crawl closer to the surface and begin feeding on the roots of the lawn again.
- In late spring to late summer, the grubs will pupate and turn into adult beetles.
- The adult beetles then mate, lay eggs, and complete the cycle.
Signs of Lawn Grub Damage and Grub Activity
Homeowners usually won’t discover a grub problem until it becomes a large infestation. Here are some of the most common signs of lawn grub damage and activity.
Brown Patches
As grubs chew up the grass root systems, they’re disconnecting the blades from their source of water and nutrients. This will inevitably cause a lawn to turn brown. Those brown patches may grow, as well, as the grubs eat the roots at the edges of the irregular patches, moving outward. Some homeowners might not even notice patches until they’re too large to miss.
Spongy Turf
Grub damage often leaves damaged lawns feeling spongy or soft, with a bit of bounce under the foot. These lawn issues might not immediately make the homeowner think of grubs, but they are a likely cause.
Turf That Pulls Up Easily
One sign of severe damage is turf that easily separates and pulls up from the ground underneath. With roots holding the soil in place, the turf can pull up like sod, or even a carpet.
Increased Activity from Animals That Eat Grubs
Noticing animals like raccoons, skunks, deer, and lots of birds turning over the grass and rooting into the soil is a sure sign of a grub infestation. These animals love grubs and know where to go for their lunch, and your yard might be the cafeteria.
Beetles Flying Around at Grass Level
Beetles flying around at grass level is never a good sign. These bugs are either emerging from the pupal stage or looking for a place to lay their eggs. Either way, where there is beetle activity, there will be a grub infestation in the future.
The One-Square-Foot Test
Another way to determine whether or not there is a grub problem is to perform The One-Square-Foot Test. This test involves using a shovel to dig up a one-square-foot section of turf in several spots in the lawn, and then counting how many grubs there are in that section. This is a helpful gauge of the grub population.
Generally speaking, a few grubs are fine (under 5), and a healthy lawn can handle these grubs. More than five grubs but less than 10 is a sign of an impending infestation. More than 10 grubs? That’s a severe infestation.
Grub Control Options
The following are some ways to control or kill grubs, and some homeowners might find that they need to use some or all of these options to take care of their grub problem.
Grub Killer
Grub killer products kill grubs instantly, and they’re useful for getting severe infestations under control quickly. These may come in liquid form but granules are most common. Once the user applies the granules to the lawn and waters them in with a hose, they’ll soak into the soil, killing grubs right away.
Grub Control
Grub control products are systemic pesticides, meaning they attack the grub while its still in the egg or its early stages. These products don’t kill grubs instantly, but they can be helpful for preventing a grub problem from occurring in the first place.
Organic Pest Control Options
There are some organic grub control options that folks can use to control lawn grubs as well. Neem oil is an effective natural grub killer, as are milky spore and beneficial nematodes. We go over all of these types of grub killers in this article.
Call a Pest Control Company
Another option is to call a professional pest control company to handle the grub infestation. These pros will be able to tell exactly which white grubs you’re dealing with, what they eat, and what pesticides to use to treat lawn grubs.
Call a Lawn Care Company
A professional lawn care company can be your best friend in the war against lawn grubs. These pros will help keep the lawn as healthy as possible, and healthy lawns stand a much better chance of surviving a grub problem. They may even have grub control services to offer. Also, a professional lawn care service will be able to dethatch and aerate the soil, making it a less hospitable home for a lawn grub.
For More Information
If you’re looking for more information about lawn grubs, be sure to check out our other articles on the topic. We’ve written blog posts on the 7 Most Common Signs of Grub Damage as well as the Best Grub Killers.
Lawn Grubs FAQs
That’s a lot of info on the grubs, but there might still be some questions lingering about below the surface. The following are some of the most common questions on the topic.
What do lawn grubs turn into?
Lawn grubs generally turn into beetles. Possible species include Japanese beetles, European chafer, or May or June beetles.
How do you get rid of grubs in your lawn?
There are a few ways to get rid of grubs in your lawn:
- Use grub control products to prevent them
- Use grub killers to kill them immediately
- Introduce natural predators to the yard
- Call a pest control company
- Call a lawn care company
What attracts grubs to your yard?
Sadly, grubs prefer healthy, thick grass. Certain types of grass, specifically ryegrass, may attract them more readily. Luckily, you also have a better chance to control grubs the healthier the grass is.
How do you know if you have grubs in your lawn?
Grub infestations damage lawns by eating the roots, and this does leave behind some telltale signs. Those signs include turf that easily separates from the ground underneath, turf that feels spongy underfoot, irregular brown patches, and the presence of natural predators like raccoons and skunks.
