Nematodes are roundworms of the Phylum Nematoda order. Most nematodes live in the soil in very large numbers and are best known as plant parasites that live in or on plant roots. However, studies are now revealing lesser-known, beneficial types of nematodes that help in pest control and the breakdown of organic matter. These nematodes are often referred to as free-living nematodes and can be found in moist soil around plants, especially around the roots of plants.

For gardening purposes, nematodes can be classified into two different types: destructive nematodes which destroy plants and beneficial nematodes which break down organic matter and feed on harmful insects.

Destructive nematodes are herbivores and were the first ones studied by colleges and agricultural experts because of their destructive nature. They push their needle-like mouthpart into the root system of plants where they feed at the root surface. Another species of plant-destroying nematodes actually enter into the root where they can live and feed.

Beneficial Nematodes

These are the nematodes that are most talked about in the organic realm. Even though most nematodes help with the break down of organic matter, the beneficial nematodes actually feed on insects that have at least one life cycle in the soil. Beneficial nematodes are not as common as the others but can be economically introduced into most soils as a form of biological control of soil-dwelling pest insects.

Beneficial nematodes are microscopic, non-segmented worms that attack soil-dwelling insects without harming plants. They enter the bodies of their host mainly through cavities and sometimes through the body wall where they reproduce, leaving their offspring to destroy the host. They can sense temperature changes caused by soil-living insects and move toward them. Gases emitted from these insects also attract beneficial nematodes in their direction. Beneficial nematodes are very effective against fleas, ants, termites, roaches, flies and grubs, some of the most damaging or pesky critters in the residential garden.

When I was reading up for this article I found that the EPA considers beneficial nematodes to be so safe that they waived the application requirements. We have had customers ask if beneficial nematodes are harmful to humans, pets and earthworms and the answer to that is: “NO!”

Insects Attacked by Beneficial Nematodes

  • Algae gnats
  • Apple leaf roller
  • Army worms
  • Banded cucumber beetle
  • Bark beetle
  • Bean leaf roller
  • Bess beetle
  • Billbugs
  • Black fly
  • Boll weevil
  • Borers
  • Cabbage looper
  • Cabbage worm
  • Cane weevil
  • Carpenter moth
  • Cockroach
  • Click beetle
  • Codling moth
  • Colorado potato beetle
  • Corn earworms
  • Corn root weevil
  • Cutworms
  • Earwig
  • European corn borer
  • Fall army worm
  • Field cricket
  • Flea beetle
  • Fleas
  • Fruit fly
  • Grasshoppers
  • Gypsy moth
  • Horn worm
  • House fly maggots
  • Imported fire ant
  • Iris borer
  • Japanese beetle
  • June beetle
  • Leaf beetle
  • Leaf miner
  • Leather jackets
  • Leather skeletonizer
  • Meal worm
  • Meal moth
  • Measuring worm
  • Melon worm
  • Mexican bean beetle
  • Mormon cricket
  • Onion borer
  • Oriental fruit moth
  • Pear aphids
  • Pear weevil
  • Pine beetle
  • Red bugs
  • Rice weevil
  • Round headed borers
  • Sawflies
  • Scarab beetle
  • Seed corn maggot
  • Sod webworm
  • Southern pine beetle
  • Southern root worm
  • Sow bugs
  • Spruce budworm
  • Squash bugs
  • Sting bugs
  • Strawberry root weevil
  • Termites
  • Thrips
  • Tobacco budworm
  • Tobacco hornworm
  • Webworms
  • White fringed beetle
  • White grubs
  • Winter moth
  • Wireworm
  • Wood borers
  • Yellow fever mosquito

Application Instructions

The main thing that you need to know about applying beneficial nematodes is that they want moisture. That is why I am making such a big deal now, with this article. The soil is cooler and we should be getting more rain, so a lot of insects are going to go into the soil now to hibernate and become easy prey.

Here in Dallas I recommend releasing beneficial nematodes at dusk. I apply them with a watering can. By doing so I do not mess around with separating the vermiculite from the actual nematodes. Since you need to let the beneficial nematodes soak in water for thirty minutes, I use distilled or dechlorinated water to assure their survival. Periodically swirl the water so that the nematodes do not settle on the bottom of the watering can.

If you want to use a pump sprayer, pour the entire contents of the package into water and break up the carrier so that the particles are evenly separated. Sift out the carrier and try to distribute this matter around the soil. Then start to spray the remaining solution over the area to be treated. Again, periodically mix the solution to keep the nematodes from settling on the bottom. Because these are live creatures and will disperse in search of food, I do not think that you have to cover every square foot, so do not worry about even distribution. BUT, you must keep the soil moist to keep the nematodes alive, especially during the first two to three weeks.