Beneficial Nematodes For Fleas

  • Written By Dan Edwards on November 10, 2018
    Last Updated: December 10, 2020

Fleas are a major nuisance for us and our beloved pets. Getting a flea infestation under control can present quite a challenge and be very stressful for us. While some pet owners are familiar with indoor treatments for fleas, fewer people realize the importance of treating their outdoor spaces.

Fleas always originate from outdoors, often from your yard, before they find their way into your home. Hence, it is super important to attend to these spaces to stop fleas for good.

There are lots of chemicals which can be used to kill fleas in your yard, but these have the potential to not only damage the environment, but also be harmful to you and your pets’ health.

Luckily, there is a natural, non-toxic and very effective solution to destroy fleas in your yard—beneficial nematodes.

In this article, we explain what beneficial nematodes are, how they work, and how to use them to eliminate fleas.

What Are Beneficial Nematodes?

Beneficial nematodes are microscopic, colorless, roundworms which have very long bodies. They naturally live within the soil, and are found in almost every habitat on earth. Beneficial nematodes are known as “entomopathogenic nematodes.”

Beneficial Nematodes
Beneficial Nematode

These creatures can be used to effectively control pest insects which live in and upon the ground, but are not able to control pests which live among plants. There are also negative, or “plant parasitic” nematodes which are so called because they attack crops and cause damage to plants.

Beneficial nematodes prey upon ground and soil dwelling pests without causing any detrimental effects to animals, plants, humans, or yard-friendly insects such as earthworms. This means that nematodes are a much safer and chemical-free alternative to other yard pest treatments.

Nematodes are more genetically and morphologically diverse than almost all other animal groups on earth. The only animal group which has more diversity is the arthropod group.

There are more than 30 different species of beneficial nematodes, with each one having a preferred host. This means that no matter what pest you’re trying to target, there will be a nematode for your needs. All beneficial nematodes have a life cycle which includes an egg stage, four larval stages, and then finally the adult stage.

Do Beneficial Nematodes Kill Fleas?

Many people believe that once they’ve treated their home, furniture and carpets for fleas, and removed them from their pet, their flea troubles are over. The inconvenient truth is that this isn’t enough to protect you from a rapid return of fleas.

flea eggs in carpet
Flea eggs between carpet fibers

These blood-sucking pests originate from outdoors. So if you do not attend to the source of fleas, your yard, you will soon be seeing them indoors again. Fleas come to be present in your yard from other animals, usually feral, urban, or stray creatures.

These animals will enter your yard looking for food or a cozy place to make a nest. Stray cats, foxes, and raccoons are the most common animals which harbor fleas among their coat.

Fleas lay their eggs upon these hosts, but the eggs are designed to drop from the host’s body as soon as they dry out. Therefore, these animals are unwittingly distributing flea eggs everywhere they roam, like a salt shaker.

flea eggs

These eggs will then develop, hatch and mature into adult fleas within your yard. Adult fleas will quickly make their way into your home on your pet, or on you and your clothing.

Nematodes are a very effective way to kill fleas in your yard. Once they come into contact with a flea host, they will often kill them within as little as 24 or 48 hours.

The nematode will find its way into the body of the flea through the anus, mouth, breathing holes or the bodily wall if possible. Once inside the body of the flea, the nematodes secrete bacteria which “digest” the insides of the flea for them to feed upon.

These bacteria multiply rapidly and kill the flea very quickly. Once the flea has been killed, the nematodes will continue to feed and multiply within the dead flea. Once the food supply runs out, the nematodes will leave the body and look for another host.

Will Beneficial Nematodes Kill Flea Eggs?

The life cycle of a flea is quite short in comparison to many other insects. The life cycle of a flea is made up of egg, larvae, pupae, and adult stages.

Life cycle of a flea

While a flea can transition from egg to adult in only 14 days, the life cycle can become delayed if subjected to extreme environmental changes. Flea eggs can lay dormant for months if the outside conditions are not correct.

As we know, flea eggs are laid upon their host and then fall to the ground, where they stay until they hatch. Most often, flea eggs will hatch into larvae within 2-12 days. These larvae will burrow into the ground, surviving by eating their shedded skin and any other organic waste matter they can.

Nematodes will not attack and kill flea eggs, but this doesn’t reduce the effectiveness of nematodes against fleas. Flea eggs hatch quickly in normal conditions and the nematodes will rapidly attack flea larvae and pupae, as well as adult fleas.

How to Use Beneficial Nematodes Against Fleas

Fleas favor damp, dark, and shaded areas. They are likely to be hiding under low bushes, shrubbery, and log piles in your yard. They hate sunlight, so will only be found in places which never get the sun.

If you have pets, fleas will almost certainly be located in the areas in which your dog or cat likes to sleep and play.

Before starting a nematode treatment, it’s a good idea to give your yard a good clean. This will enable you to reach places which have been sheltered by leaves, logs, detritus, and any unused furniture.

Sweep away any loose leaves, move wood piles to a sunlit area if you have one, and trim grass and foliage back.

Because nematodes live in the soil, nematode treatment isn’t very effective on patios or decking. So, during the treatment, you can use these areas to store anything which would normally be on your lawn.

Nematodes come in a package or a plastic tub. This keeps them protected until you are ready to apply them to your yard. A pack of beneficial nematodes usually contains about 10 million nematodes, which is more than enough to cover an area of about 2-3000 square feet.

If you have a small yard, you can use a heavy application or keep some of the nematodes back for another time. Certain times of year are better for using nematodes than others. The optimal seasons are spring and early fall.

These times of year are when the soil temperature is generally above 50° F. You can also use nematode treatment at the end of summer to ensure any surviving fleas have been completely eradicated.

Nematodes will perish in strong sunlight and heat, therefore it is advised to apply them either early in the morning or after sunset. They need to be mixed with water before use. The ratio of nematodes to water varies with the amount of nematodes you have, but the packaging will detail how to prepare them, so just follow these instructions.

Once you have done this, you can transfer the solution to a watering can or use a pump sprayer to distribute the nematodes around your yard and across the lawn.

While it’s completely safe to use your yard and lawn immediately after application, it’s a good idea to give the nematodes time to burrow into the soil, settle in, and start attacking the fleas. For this reason, we suggest not using your yard for about 12 hours after application.

Nematodes will live for many weeks. Once they have penetrated a flea host, they will kill the flea in about 48 hours. Therefore, you should begin to see a difference in the flea population within a day or two. You do not need to continuously apply nematode solution to your yard.

Nematodes will multiply naturally within the dead flea’s body, emerging out into the soil after about 20 days. Once they have run out of hosts to feed on, the nematodes simply starve, die and decompose.

Beneficial nematodes are not in any way harmful to you, your pets, birds or yard-friendly wildlife like earthworms. They will not cause any damage to your flowers, bushes, shrubs. or trees either. Beneficial nematodes will only eat the unwelcome pests in your garden, leaving everything else alone.

The bacteria within nematodes is also harmless to humans and animals even if a nematode is accidentally consumed. Therefore, nematodes are a completely safe, pesticide-free method to use around your vegetable patch or herb garden.


The battle against fleas doesn’t end in the home. Your domestic flea problem has originated outdoors in the yard, and therefore this is where you have to hit them the hardest.

Flea eggs are deposited in the yard from feral and wild animals. These eggs quickly hatch and the adult fleas leap upon your pet, hitching a free ride into your home. Before you know it, you have an unwelcome flea infestation causing much distress to you and your pets.

While there are a number of chemical and pesticidal options for killing fleas in the yard, these present a risk of environmental damage, as well as potentially harming yard-friendly insects.

As we have seen, beneficial nematodes are a fantastic, green alternative in the fight against fleas. These microorganisms effectively target and kill fleas, larvae, and pupae rapidly and safely.

They are not dangerous to humans, pets, or beneficial wildlife, and are able to reproduce naturally once applied. We are sure you will agree that beneficial nematodes are one of the best methods to protect your property from the menace of fleas.