Beneficial nematodes

What are nematodes?

Nematodes, commonly referred to as roundworms, are a diverse group of worms belonging to the phylum Nematoda. Nematodes are characterized by their unsegmented, cylindrical bodies, and they come in a variety of sizes, ranging from microscopic to several inches in length. Nematodes play various roles in ecosystems. Some are free-living, feeding on organic matter in soil or water, and are essential for nutrient recycling. Others are called parasitic nematodes, infecting plants, insects, animals, or humans. There are about 25.000 named species, but estimated numbers of species are in the millions. Nematodes are also referred to as roundworms, threadworms, and eelworms.

Types of nematodes

In agriculture the most important types of nematodes are parasitic nematodes. More specifically insect-parasitic nematodes and plant-parasitic nematodes.

Insect-parasitic nematodes

Insect-parasitic nematodes, often referred to as entomopathogenic nematodes or beneficial nematodes, are a group of parasitic nematodes that have a unique relationship with insects. These nematodes are natural predators of various insects and play a crucial role in biological pest control, making them beneficial for agriculture and horticulture. These nematodes are not harmful to humans, animals, or plants but are highly effective in controlling harmful insects.

Plant-parasitic nematodes

Plant-parasitic nematodes are a group of parasitic nematodes that infest and damage plants, leading to significant agricultural and horticultural problems. These nematodes are detrimental to crop health and can cause yield losses. They feed on plant roots, disrupting the plants' ability to take up water and nutrients, which ultimately affects their growth and productivity.

The most common types of plant-parasitic nematode are root-knot nematodes, cyst nematodes, lesion nematodes, spiral nematodes and dagger nematodes.

Beneficial nematodes for pest control

Nematodes for pest control, often referred to as entomopathogenic nematodes or beneficial nematodes, are microscopic roundworms that serve as natural agents for biological pest control. Beneficial nematodes are highly specific in their choice of hosts and do not harm beneficial insects, humans, or animals. Common pests targeted by these nematodes include various larval insects like grubs and weevils (Coleoptera larvae), caterpillars (Lepidoptera), fly larvae (Diptera), Thrips (Thysanoptera) and many other soil-dwelling pests. 

Benefits of nematodes

Using beneficial nematodes for pest control offers several key benefits:

  • Fast-acting biological solution
  • Resistance proof - pests cannot build resistance
  • Can be applied with regular spray equipment
  • Compatible with most pesticides
  • Leaves no residue

What pests do nematodes control?

Beneficial nematodes are effective biological agents for controlling a wide range of harmful insects and pests. Nematodes are the natural enemies of grubs and weevils, caterpillars, thrips, wireworms, leatherjackets and a large group of fly larvae, such as fungus gnats, crane flies, shore flies, onion flies and more. Nematodes are a perfect fit within IPM programs due to their compatibility with most pesticides. They reduce the reliance on chemical pesticides and promote sustainable and eco-friendly pest management practices. Here are some of the common pests that beneficial nematodes can control:

Play

How do nematodes work?

Beneficial nematodes use a fascinating strategy for parasitizing and killing their host insects. Here's how they work:

  1. Seeking out hosts: Entomopathogenic nematodes actively search for potential insect hosts. They are attracted to their hosts by detecting chemical cues emitted by the insects, such as carbon dioxide, heat, and specific chemicals.
  2. Host penetration: Once they locate a suitable host, the nematodes enter the host's body through natural openings, such as the mouth, spiracles (insect breathing tubes), anus or soft cuticle areas. Some nematodes release enzymes to help digest and soften the host's cuticle, allowing them to enter.
  3. Symbiotic bacteria release: Once inside the insect host, the nematodes release symbiotic bacteria, such as Xenorhabdus or Photorhabdus species, into the insect's body cavity. These bacteria are essential for the nematode's parasitic strategy. The bacteria quickly multiply, causing septicemia (a lethal blood infection) in the host insect.
  4. Bacterial infection: The bacteria secret toxins and antimicrobial compounds that kill the host insect within a few days. The host becomes immobile and eventually dies due to the bacterial infection.
  5. Feeding and reproduction: The nematodes feed on the multiplying bacteria and absorb the nutrients released by the bacterial activity. This provides nourishment for the nematodes and supports their reproduction. As the bacterial population within the host insect continues to grow, so do the nematode populations. The nematodes reproduce, developing through multiple juvenile stages into mature adults.
  6. Emergence: After consuming the host insect's tissues and the bacteria, thousands of new nematodes emerge from the dead insect's body. These newly emerged nematodes are now ready to seek out new hosts and continue the cycle.

Beneficial nematodes species

Several species of beneficial nematodes are commonly used in biological pest control. These nematodes play a vital role in managing insect pests and are considered beneficial for agriculture, horticulture, and integrated pest management programs. Some of the well-known beneficial nematode species include:

  • Steinernema feltiae: These cold tolerant nematodes are effective against a wide range of soil-dwelling pests, including fungus gnats, vegetable root flies, root weevils, and other insect larvae. They are commonly used in greenhouse and nursery pest management and are becoming more and more popular in orchards and outdoor vegetable crops.
  • Steinernema carpocapsae: This species is known for its effectiveness against pests such as wireworms, various caterpillars, and weevil and beetle larvae. Its ability to adapt to different temperatures makes it a good choice for controlling caterpillars in various crops.
  • Heterorhabditis bacteriophora: These nematodes are particularly effective against soil-dwelling insects like Japanese beetle, white grubs, and root weevils. They are used in turfgrass management and for controlling pests in several vegetable crops, blueberries, and other soft fruit crops.

How to apply nematodes

The application of beneficial nematodes is a straightforward process that ensures they come into contact with the target insects. Nematodes can be applied by foliar or soil application, depending on the target pest. Here's a general guideline on how to apply nematodes (always check the label for detailed application advice):

  • Choose the right nematode species tailored to your specific pest problem
  • Determine the required nematode quantity based on the infestation severity and treatment area and as indicated on the product labels
  • Store nematodes in a refrigerated environment to maintain their effectiveness until the day of application
  • Create a nematode suspension by mixing them with water following provided instructions
  • In case of soil application: Ensure the soil or growing media is adequately moist (not waterlogged) to facilitate nematode movement. Also take the soil temperature into account (see product labels for detailed information)
  • In case of foliar application, the air relative humidity is another important factor to consider to maximize success (>75%)
  • Ideally, apply nematodes during periods of moderate UV light, such as early morning or late afternoon, and avoid high sun intensity
  • Spray nematodes evenly using various methods like sprayers, irrigation systems, drones etc. to help nematodes reach pest larvae
  • Consider follow-up applications based on pest severity and nematode species
  • Monitor and adjust your treatment plan as needed

Success stories

Frequently Asked Questions

Nematodes - Application

Nematodes - Regulations

Nematodes - Packaging and formulation

Nematodes - Storage