Nematodes are the most numerous multicellular animals on Earth; in fact, there are many thousands of individual nematodes in every single handful of garden soil! They’re so small, you can’t see them with the naked eye – you need a 10X hand lens. So every time you dig in the soil, you’re touching these little guys. But what are they?

Fungus gnat

Fungus gnats are a common problem in houseplants and seedlings. Beneficial nematodes are an excellent way to control them organically.

Photo Credit: ©2005 Buglady Consulting.

White grub

Beneficial nematodes can help control grub populations.

Photo Credit: ©2001 Buglady Consulting

Nematodes are microscopic nonsegmented worms that can be free-living, predaceous or parasitic – or you could look at them as being good, bad or indifferent. The bad nematodes can parasitize roots of plants, cause foliar damage or even be parasites of mammals. Then there are the indifferent ones – they just hang out in the soil feeding on things like bacteria and fungi. Finally, there are the good guys: These are the nematodes that are used in modern biological control to combat a wide variety of insect pests. They’re also referred to as entomopathogenic nematodes.

Using nematodes for biological control isn’t a new development. Back in 1929, researchers were already working with them, but with the advent of chemical pesticides, this technology went by the wayside. In recent years, with concerns of pesticide exposure and pests becoming resistant to sprays, researchers turned to Mother Nature for help. One of her little helpers being used today is the beneficial nematode.

Beneficial nematodes can be broken down into two ways in relation to how they hunt prey:

First, there are the “ambushers” (which include the Steinernema spp.). This group of nematodes sits and waits for an insect host to move by and then moves to force their way into the host’s body. They’re very effective against pests moving around on the soil surface, such as cutworms and fungus gnats, to name a few.

The second group consists of the “cruisers.” These nematodes move around actively searching for hosts. They’re usually found deeper in the soil profile, attacking many types of grubs. These are normally in the class Heterorhabditis spp.

On the commercial market today, there are several species of beneficial nematodes available through the Internet. They can be used to control grubs, fleas, weevils and many other insect pests. They key is the pest must spend part of its life cycle in the soil, where the nematodes are applied. So it’s essential to know what your pest is before you can properly treat the problem. Before you order nematodes, talk to the supplier and find out what species of nematode is right for you and your conditions.

Beneficial nematodes can be an excellent tool in the lawn and garden to control certain pest insects. They can be used with organic gardening and are safe for kids and pets.