What is a Grub Worm and How to Control Them

Have you noticed little white grubs in your soil? White grub worms are a huge nuisance in many homeowner lawns found throughout the United States. Take a deeper look at the grub worm, one of the most notorious pests in home lawns, in the article below. Once you know more about the grub worm and you’re able to accurately identify an infestation, you can then begin strategizing ways to get rid of them and prevent future infestations. 

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What are grub worms?

Many may be wondering, “What is a grub worm?”. First off, it is important to know that grub worms, the larvae form of scarab beetles, can be found in many lawns and gardens of North America—especially in Florida’s humid temperate conditions. Since Florida doesn’t endure harsh winters, grub worms can thrive and multiply all year long.

Grub worms, also called white grubs, can be found in the soil damaging lawns by feeding on the roots and thatch of turfgrass. Although they’re called grubs, they’re actually considered an insect as they have six little legs located near the head of their bodies. Certain species can remain in their larval stage for 2–3 years while some species live as grubs for only one year before pupating and turning into a beetle.

What do grub worms turn into?

At the adult stage, grub worms turn into beetles that emerge from the soil. The type of beetle species varies based on the type of grub worm present. You may begin to notice beetle damage as they eat the leaves of your grass and other plants in your garden.

The May or June beetle will first live as grubs in the soil for about 2–3 years while other species may only remain grubs for a single year before turning into a beetle. Some of the species of adult scarab beetles include:

• Japanese Beetles
• June Beetles
• May Beetles
• Masked Chafers

What does a grub worm look like?

All grub worms have bodies that curve into a C-shape with yellow-brown heads. They have six legs located near the front of their bodies and a dark-tinted abdomen due to soil particles showing through their exoskeleton.

A grub worm’s length can range depending on the species of grub worm. They are usually a quarter inch to two inches in length, and are easy to identify with their cream-colored bodies. 

What do grub worms feed on?

Grub worms feed on the roots of just about any warm and cool season turfgrass types which in turn damages the grass and in certain instances, kills it completely. They don’t have much of a preference between the types of turfgrasses to feed on.

Grub worms can be found feeding on the roots of bermuda grass, zoysia grass, bahia grass, centipede grass, Kentucky bluegrass, tall fescue, St. Augustine grass and more. There is not a grub worm resistant, living turfgrass.

How do grub worms damage grass?

During the larval stage of their lifecycle, grub worms live underneath the soil’s surface and feed on the roots of turfgrass. The roots are the primary way for turfgrass to obtain water and other nutrients.

Without roots, grass will die. Grub worms will damage grass but in severe cases, they can completely kill an entire lawn. 

What time of year do grubs damage lawns?

Grub worms can be found just about anytime of the year, however this can sometimes vary depending on your geographic location. Most of the symptoms of damage will usually appear early in the year around the spring season or later in the fall.

If you have a heavy infestation in the spring, your grass may take a little longer to green up. This is a good indication of a grub worm infestation. In the later parts of the year on the other hand, you may notice that an entire patch of your lawn has died. This leads us to the next question: how do you identify a grub worm infestation?

How do I identify a grub worm infestation?

Diagnosing a grub worm problem can be difficult if you don’t physically spot a grub worm. This is because they live underground. Symptoms of an infestation include general thinning or yellowing of turf, which is very similar to other pest infestations like chinch bugs, for example, drought or nematodes. 

One way to determine a grub worm infestation is to step on the turf in the spring and see if it feels spongey or bouncy. You can also try lifting the sod and see if it comes up like a carpet. This means the roots have likely been destroyed. 

The best way to diagnose a grub worm infestation is to get your hands dirty—get a shovel, dig under the soil and see if you spot any grub worms. 

How do I treat a grub worm infestation?

Cultural Control

The best way to control grub worms with cultural practices involves keeping a healthy, well-maintained lawn. Follow a seasonal maintenance schedule for your grass type, make sure its growing in healthy soil, install new grass properly, select the right grass for your area, aerate, dethatch, mow and water appropriately.

A thick, healthy lawn can better withstand external stress caused by insects and pests. One way to keep a healthy, thriving lawn is to fertilize it with the nutrients it needs.

You might want to consider a fertility program such as Lawnifi®. Lawnifi is a fertilizer program designed to give your lawn the nutrients it needs when it needs them. Subscribe to receive seasonal Lawnifi fertilizer boxes throughout the year, or purchase each seasonal box individually.

Lawnifi also offers a granular formulation called Lawnifi Foundation for those who prefer traditional granular fertilizer.

You can learn more about Lawnifi at lawnifi.com or by reading Why Use Lawnifi Fertilizer?. However, this does not guarantee 100 percent grub worm resistance.

Chemical Control

If your lawn’s damage is severe and the grub worms are not manageable with cultural methods, you can use a chemical treatment instead. There are products available to the homeowner that will kill grub worms.

Some effective active ingredients for curative treatment include Chlorantraniliprole, which can be found in Scotts GrubEx, Imidacloprid, which is often found in Merit 0.5 G, Merit 2F  or Lada 2F and Triclorfon, which can be found in Dylox 6.2. Imidacloprid products can be used for both preventative and curative control while GrubEx and Dylox are used as curative control products.

Dylox 6.2 is a fantastic product to use on severe grub worm infestations because it works against second and third instar grub worms on contact. As previously mentioned, some grub worm species, like those of the May and June beetle, live for 2–3 years before turning into a beetle. Other grub species only last for a year.

Certain products that work on annual grub worms might not work on grub worms that live for multiple years. Dylox 6.2 will kill grub worms regardless of where they’re at in their lifecycle. 

Be sure to read and follow application instructions for each product thoroughly.

How do I prevent grub worms?

If you are worried about grub worm infestations in your lawn, apply an insecticide preventatively. This usually consists of one application a year and then you don’t have to worry about it for the rest of the year. Use the same products above and follow application instructions. 

If you were able to out-rule grub worms as a problem but ran into a different kind of insect or pest, learn more about insect identification here: Insect Identification.