Do Nematodes Kill Earthworms? (or Are They Beneficial?)

Worried about nematodes taking a bite out of your beloved earthworms? There are a few things you need to be cautious about when it comes to mixing your wigglers with anything that’s rampant in your garden.

Many of us do not know how important these little creatures are to the health and maintenance of our land. Thankfully, more and more people are realising just how important earthworms are to our eco-system! But what about the other organisms dwelling in our soil? Which ones are good and which ones are bad? 

No, nematodes do not kill earthworms. These soil borne insects appear in many different shapes and form. In fact, many people think of them at their larval stages, but they generally will not kill worms.

When it comes to naturally occurring organisms in our very own gardens, the number of different species can be quite overwhelming.

There are so many different kinds of creatures with different kinds of roles, all that play a part in the grand scheme of things.

Keep reading, and we’ll fill you in on why you probably won’t need to worry about nematodes, at larval or grub stage.

Do nematodes kill garden worms?

No, nematodes do not kill garden worms. In fact, applying beneficial nematodes could be very good for your garden! They are, on the whole, considered beneficial organisms.

First of all, it is important for us to understand more about what exactly nematodes are. 

There are many species of nematodes out there, all with their different roles and tastes. What is it that makes these organisms beneficial to our greenery and soil?

You may have heard that they are like worms but really only in shape.

They indeed are very small, with long bodies, but do not have segmented shapes, the way the other worms do. They also tend to be very clear and pale in color. 

There is a distinction to be made between two large groups of nematodes: 

  • Entomopathogenic nematodes, also known as beneficial nematodes;
  • Damaging nematodes, such as ectoparasites and endoparasites. 

As you can imagine from the name, beneficial nematodes pose absolutely no threat to earthworms!

They eat other micro-organisms and pests that can be damaging to plants and gardens, and have nothing to do with earthworms. 

Thankfully for the earthworms, even the damaging nematodes pose more of a threat to plants and live vegetation than they do to wrigglers.

Of course, for all of you gardeners out there, they can still be a bit of a pain. 

Are nematodes bad for your garden?

Some are, some aren’t. However, insect parasitic nematodes can be beneficial.

There are over 30 different species of beneficial nematodes, all with their own superpowers that they bring to your garden.

Nematodes are great for controlling numerous insect pests such as beetles, caterpillars, cutworms, crater flies, grubs, corn rootworms, etc.

They do not adversely affect any beneficial insects such as earthworms, or any other living organisms.

Beneficial nematodes infest grubs and other insects with a specific kind of bacteria. The nematode carries Xenorhabdus sp., a bacteria that kills the pest insects – after two days, the nematodes feed on the dead insect’s body. 

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Although it may sound a little harsh, it is extremely beneficial and is a completely natural way for gardeners to deal with their pests.

That is why nematodes have becomes an increasingly popular source of natural pesticide, and can be purchased online or at most gardening centres.

They come mainly in a form of spray which can be simply sprayed in the areas where you most need them. 

In order for the nematodes to thrive, it is essential that you spray them onto your desired area when it is warm outside, and in a damp area. 

Do not forget to use the spray over time. Simply placing the bottle in storage for over a year will kill the nematodes and be rendered useless to you.

What will nematodes kill?

As mentioned, beneficial nematodes, also known as the insect parasitic nematode species, will kill and eat the common parasites that we find in our gardens.

Other pest insects that they feed on include:

  • cabbage root maggot
  • Colorado potato beetle
  • flea beetles
  • raspberry crown borer
  • corn root worm
  • artichoke plume moth
  • strawberry root weevils
  • corn earworm
  • the flea beetle
  • Japanese beetle
  • white grubs
  • thrips
  • fungus gnats
  • fly larvae
  • and the list of garden pests goes on!

Plant parasitic nematodes, however, are an insect species with an entirely different diet.

When it comes to ectoparasites, they do not feed on a dead pest but rather use their stylets to drain the roots of plants, seeking out their nutrition. 

Endoparasites, on the other hand, insert themselves either partially or entirely, into the plants.  Sadly, this kind of feeding on a plant will begin to show over time. 

Another issue that comes from this type of nematode is that they usually do not work alone.

Once they have inserted themselves into a plant, other bacteria, fungi and insects attack the plant, damaging it further. 

It is important to also know that nematodes carry certain kinds of toxic bacteria that infect plants.

You will be able to notice the damage from a nematode if your plant begins to wither.

If it looks like a plant that has been starved of water and other nutrients, even though you have been watering it accordingly, then chances are that the nematodes are preventing your plants from getting the water and nutrients that it needs to survive. 

How long does it take for beneficial nematodes to work? 

Unlike chemical pesticides and other pest control methods, which leave insect bodies behind, nematodes consume the bodies of the pests, making it hard for us to distinguish when exactly the beneficial nematodes have begun to work! 

As long as you properly place the nematodes in your garden (nematodes seek warm, moist soil), and keep the area suitable for them, so keeping it warm when you can and nice and damp, then the nematodes should be doing their jobs over the course of a week.

Although that is a very brief period of time and you may therefore not yet be certain of their efficiency, give it 2 to 4 weeks maximum, and you will definitely be able to notice a difference! 


Hopefully you will now be able to see that your earthworms aren’t in danger from nematodes and in fact, they often work symbiotically with worms and affect their predators.

You should now see how beneficial nematodes are to your garden – they help us in ways that we do not tend to notice. What’s more, they won’t harm your earthworms.

If you are looking at a completely biological control of agricultural pests all whilst maintaining the health and safety of the other soil inhabiting insects and those that live on the soil surface, then why not consider buying some beneficial nematodes? It’s a great, natural way of soil pest control.