Do Beneficial Nematodes Kill Earthworms? (Answered)

When it comes to gardening and pest control, there’s an underground army that often goes unnoticed – beneficial nematodes. These tiny warriors are hailed for their effectiveness in controlling garden pests, but what about our beloved earthworms? Do beneficial nematodes harm these gentle earthworms?

In this article, we’re going to dig deep and explore the intriguing relationship between beneficial nematodes and earthworms. Buckle up because there’s a lot more to it than meets the eye!

What Are Beneficial Nematodes?

Nematodes are microscopic roundworms found nearly everywhere on Earth. Over 25,000 species have been identified so far.

Many nematodes are parasitic and cause diseases in plants and animals. But some are beneficial predators that help control pest insects.

The most common beneficial nematodes used in gardens are:

  • Steinernema -Attacks soil-dwelling insects like fungus gnat larvae
  • Heterorhabditis – Also controls soil pests
  • Neoplectana – Seeks out cutworms, armyworms, and other caterpillars

These nematodes are available for purchase and can be applied to soil or turf areas to reduce pest populations. They occur naturally in soil but adding more can boost their effectiveness.

do beneficial nematodes kill earthworms
do beneficial nematodes kill earthworms

Do beneficial nematodes kill earthworms?

Earthworms are often considered the gardener’s best friend. Their tunneling aerates soil and their castings enrich it. That’s why gardeners want to avoid anything that could potentially harm these helpful worms.

So an important question arises – do beneficial nematodes kill earthworms?

The short answer is no, beneficial nematodes do not kill earthworms. In fact, they can coexist quite peacefully. Here’s a deeper look at the relationship between these two soil-dwellers.

Why Beneficial Nematodes Don’t Harm Earthworms?

There are a few reasons why beneficial nematodes leave earthworms alone:

  1. They have different food preferences.

Beneficial nematodes prey on soil-dwelling insects, not earthworms. Once they deplete the insect pest population, they die off themselves.

Earthworms primarily consume decaying organic matter. While nematodes are carnivores that only eat living creatures. They have no interest in decomposing leaves, roots and other materials that earthworms feast on.

  1. Their life cycles don’t overlap.

Beneficial nematodes only live about 2-3 weeks in soil. When the temperature falls below 50°F (10°C) or rises above 95°F (35°C), they become inactive.

But earthworms can live 1-2 years. They remain active in soil year-round in most climates.

So for much of the year, beneficial nematodes aren’t even present when earthworms are active.

  1. Earthworms avoid nematode-treated areas.

Some research indicates earthworms may temporarily avoid areas where high concentrations of beneficial nematodes have recently been applied.

This suggests earthworms can detect and avoid nematodes. But they repopulate treated areas once nematode levels decline.

Do Nematodes Have Any Negative Impacts on Earthworms?

While beneficial nematodes don’t directly harm earthworms, their use can lead to indirect effects:

  • Reduced food supply – If nematodes wipe out insect larva and grubs, it temporarily decreases this food source for earthworms.
  • Disruption of tunnels – As nematodes move through soil seeking prey, they may collapse existing earthworm tunnels and burrows. This forces earthworms to expend energy reconstructing their paths.

However, these impacts are temporary and localized. Overall, coexistence with beneficial nematodes doesn’t appear detrimental to earthworm populations.

Related guide – Does neem oil kill earthworms on plants?


Earthworms and beneficial nematodes may seem like very different creatures, but they actually have the potential to coexist in harmony in the soil environment. While nematodes hunt down and consume insect pests, earthworms focus on breaking down organic material. With their differing food sources and life cycles, nematodes pose little threat to earthworm populations.

Gardeners can confidently use beneficial nematodes for natural pest control, knowing these microscopic helpers won’t negatively impact the earthworms that aerate and enrich the soil. With the right conditions, these two soil allies can work together to create a healthy below-ground ecosystem, supporting abundant life in the garden.

Reference official guide

Are beneficial nematodes harmful to earthworms?

No, beneficial nematodes do not harm earthworms. They have a high specificity for targeting certain pests and insects, while earthworms have different physiological characteristics that make them less susceptible to the actions of beneficial nematodes.

Do beneficial nematodes and earthworms interact in the soil?

Beneficial nematodes and earthworms have limited interaction in the soil. Beneficial nematodes tend to inhabit the upper soil layers, while earthworms primarily reside in deeper soil horizons. As a result, direct contact between the two is minimal.

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