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Photo Credit: ©2005 Buglady Consulting.

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

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.