“Lawn Grubs - When and How to Get Rid of Grubs”

Lawn grubs feed on grass roots. They are predominantly found feeding on cool-season grasses such as Kentucky Bluegrass, Rye and Fescues.
A few here and a few there will not ruin your lawn. Once you have five or more per square foot of lawn it is time to take action. If you don’t, you will have birds, skunks, raccoons and moles hunting for dinner in your grass.

Lawn Damage caused by these insects can be even more destructive than the damage caused by these pests.

“What are Grub Worms?”

They are the larvae of large dark colored beetles such as Japanese Beetles, May Beetles and June Beetles. 

They have distinctive characteristics:

  • They are ¼ to ¾ of an inch long
  • They are “C-Shaped”
  • They have white bodies
  • Their heads are brown
  • They have 3 small sets of legs near their heads

As adults, their appearance varies because they are the larvae of several different beetles:

Japanese Beetles

  • 3/8 of an inch long
  • Shiny shell that is metallic green with copper brown wing covers
  • Patches of white on both sides of their body
  • White hairs on their stomachs

May and June Bugs

  • Larger than the Japanese Beetle, usually ¾ of an inch long
  • Dark burgundy color
  • Brown hair on their abdomen.

From Lawn Grubs to Insect Damage

“What is their Life Cycle”

  • They overwinter as larvae deep in your soil.
  • In early Spring, they move closer to the surface of your soil to feed on grass roots.
  • In late Spring or Early Summer, they pupate into adult beetles that feed above the ground on other plants.
  • The beetles mate and lay eggs in your soil.
  • In late Summer or Early Fall, the larvae hatch and move deep in the soil to feed on the grass roots

The process continues over and over again.  The larvae stage, when they are white grubs is by far the most harmful stage for your lawn.

“What are the Signs That You Have White Grubs?”

There are several sure signs that they have invaded your soil.

  • Irregular shaped patches of dead brown grass (usually in late Spring or early Fall)
  • The grass lifts right up because there is nothing left to anchor it into the ground. They have eaten the grass roots.
  • Birds, moles, raccoons and skunks have caused extensive lawn damage hunting for them.
Grub Damage More Grub Damage Animals digging up Lawn Grubs
You can see that the grass has turned brown in odd shaped patterns due to the infestation of lawn grubs. The grass peels back like carpeting in areas that are infested with lawn grubs. Damage that birds, skunks, moles and raccoons have caused hunting for their favorite dinner, grub worms.

“How to Detect That You Have Lawn Grubs”

An old lawn care trick will help you determine if your lawn is infested with white grubs.

At dusk, drench the affected areas with water. Next morning, take an old coffee can without a lid. Turn the can upside down and place it on the problem area. Dig 5 -6 inches deep into the soil and pull the grass back.

If  you have them, you will see them.

Another trick if you have a damaged area near concrete, pull the grass back.  If you have them, they will congregate here because they cannot go beyond the concrete wall.

Once you have 4 -5 white grubs per square foot it is time to spring into action. 

“How to Get Rid of Grubs in Your Lawn”

There are several methods you can use to eliminate them from your lawn: biological control, botanical pesticides, insecticidal soaps, synthetic chemical control and preventive measures.

Biological Control

With this type of control you fight one living organism with another. Your goal is to increase the numbers of organisms that already live in your lawn to better fight off the lawn pests. When your pest problem is eliminated, the micro-organisms return to their natural levels because there are no more pests to feed on. Beneficial Nematodes - Micro-organisms that prey on certain lawn pests. They attack the pest when they are at their most damaging stage. Read the packaging for exact directions and warnings, but basically all you do is:
  • Mix with water
  • Apply to a damp lawn
  • Leave them to do their job
This will typically kill them within 24 – 48 hours. For the most effective results, check the shelf life and best time to apply to the turf on the packaging. Milky Spore (Bacillus popilliae) - This is a bacterium that will kill them. It creates a protective blanket on your lawn. It will kill lawn grubs in 7 – 21 days. The lawn grub decomposes in your soil and it releases billions of new spores to protect your grass. The results can be long term. The manufacturers may include a guarantee that this product will work for up to 10 years if used as directed on the packaging. Milky spore is not harmful to beneficial insects, pets and humans. Milky Spore can be purchased at your local lawn and garden center or on-line. Depending on the size of the package, the cost can range from $20 - $35. Learn more about milky spore here. Insect Control: Grub Control Milky Spore 10 oz

Botanical Pesticides

Made from plant materials and less toxic to you and your pets than it’s synthetic counterpart. This type of pesticide works better on the adult beetles because it breaks down quickly and must immediately come into contact with the pest. Think of it this way, get rid of the adult beetles and you won’t have to worry about the lawn grubs. Neem Oil Extract comes from a tropical evergreen tree, the Neem Tree. It is widely known to repel Japanese Beetles.

Insecticidal Soaps

Made from the salts of fatty acids. They work best when mixed with water and applied with a sprayer. They are biodegradable and non-toxic to humans.

Synthetic Chemical Pesticide

Most commonly used and the quickest to control pests. Effective in killing lawn pests, but may also kill the beneficial insects in your lawn. Pesticides can also be toxic to you, your family and your pets.
Important warning when applying chemical pesticides
  • Always read the label carefully before using a pesticide. It is there to keep you, your family and pets safe.
  • Follow the instructions exactly as indicated on the label. They are there for a reason.
  • Wear protective clothing (gloves, goggles, shoes, long pants and long sleeve shirts)
  • Dispose of containers and leftovers in a safe manner.
  • Keep children and pets away from any pesticides you have stored.

There are many types of synthetic chemical controls that you can purchase at your local lawn and garden center or on-line. All can be applied with a spreader (fertilizer cart). It is best to use a different spreader when applying pesticides rather than the one you normally use to fertilize. Be sure to water well after the application so that the chemical soaks deep into the soil. Scott’s Grub-Ex will control them for the entire season (Spring-Summer). This product contains a pesticide known as Chlorantraniliprole. The newer version of this contains 60% less active ingredients, but kills up to 25% more of these lawn pests than previous versions. Bayer Advance Grub Killer – The active ingredient contained in this pesticide is Trichlorton. A 10 lb bag covers up to 5,000 square feet. Costs approximately $18. Sevin – The active ingredient contained in this pesticide is Carbaryl. A 10 lb bag covers up to 5,000 square feet. Costs approximately $15 - $18. Store Brand – The active ingredient contained in this pesticide is Imidacloprid. A 15 lb bag covers up to 5,000 square feet. Costs approximately $16.

Preventive Measures

There are also preventive measures you can take to keep them away if you have had them in the past. Practicing good lawn care maintenance is a great way to keep them out of your lawn.
  • Remember to mow high (keep grass over 2 inches in length).
  • Overseed your lawn to keep it thick. Japanese beetles prefer to lay eggs in sparse thin lawns.
  • Water your grass less often and deeply. This promotes deep root growth. The eggs need plenty of moisture to hatch. Don’t over water your grass.

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Lawn Grub - Milky white body with 3 sets of legs near it's head.

A fertilizer cart can be used to apply synthetic chemical pesticides. The packaging will tell you the appropriate spreader settings for your application. It is best not to use your normal fertilizer cart when applying  pesticides.