natural pest control

Using Beneficial Nematodes In The Garden

using beneficial nematodes in the garden

Beneficial nematodes have been a favorite natural pest management solution of mine for years. As my houseplant collection grew in college, I began to deal with swarms of fungus gnats. After trying all kinds of traps and treatments with limited success, I broke down and invested in beneficial nematodes. They didn’t work overnight, but within days all of the fungus gnats were gone and they didn’t come back for a very long time. Beneficial nematodes are completely natural and pests don’t build up a resistance.

It was only in recent years that I discovered how valuable they can be in the outdoor garden. While the first nematodes I ordered were surefire stopgaps for controlling fungus gnats, there are a number of types of beneficial nematodes that together cover nearly the whole gamut of pests that plague the garden. These scenes of tomtatillos that looks like they were fired on by a shotgun should be in the rear view very soon.


Beneficial nematodes – a little background

The types of beneficial nematodes used for natural pest control are microscopic colorless non-segmented round worms. They occur naturally in soils throughout the world. There are a handful of species that are used to target different species of insects that plague the garden. These organisms are parasitic towards many different types of garden pests during their larval or pupal stage of growth. Some species of beneficial nematodes even have the ability to attack above ground adults, nymphs, and larvae.

The beneficial nematodes enter their host through an opening in their body. Once inside, they quickly multiply then release a bacterium whose toxin kills the host. This poisons the host’s blood and kills them within days. Then, the nematodes move on in search of new hosts. I usually start to notice pretty significant decreases within a week of applying it. In some more serious situations, multiple applications are necessary.


Natural pest control

Beneficial nematodes are sold under a variety of trade names. It is important to understand which species of beneficial nematodes attacks the pests needing to be controlled. These types of nematodes can’t develop within vertebrates, so they are safe around people and animals.

Types of beneficial nematodes:

Steinernema  feltiae
Fungus gnats, ticks, thrips, leafminers, caterpillars, cutworms, cockroaches, armyworm, cabbage maggots, corn earworm, cucumber beetle, fly larvae, fruit fly, mole crickets, and more.

Steinernema carpocapsae
Armyworm, cutworms, fleas, peach tree borers, root weevils, caterpillars, soldier ants and termites

Heterorhabditis bacteriophora
Asparagus beetles, cucumber beetle, potato beetle, june bugs, Japanese beetles, queen ants and termites

Buying and storing nematodes

I have used a handful of different brands and they were all successful when used soon after purchase. We have had success using Biologic’s Scanmask (S. feltiae). Lately, we have really liked using Arbico Organics. They carry all three types of beneficial nematodes talked about above and offer any size you could need at a reasonable price. The nematodes ship quickly and have always arrived safe and sound.

After your order of beneficial nematodes ships out, they should arrive in less than 48 hours. As soon as possible upon arrival, refrigerate the nematodes (38-42 °). Pay attention to the expiration date somewhere on the package.

Using beneficial nematodes

The majority of beneficial nematodes are applied as a soil drench or powdered form used as a spray. What is most important in applying nematodes is doing it in the right environment. Nematodes are very sensitive to UV rays, so they are best applied in filtered sun or near dusk. The area that the nematodes are being applied to should be moist before applying them and then watered in well after the application.

In order to determine the amount of nematodes to mix in the sprayer, we do a test run. I fill the sprayer up completely and spray our gardens noting where I begin and where I run out. Then, I measure the area to get the square footage. Then, I portion the nematodes out accordingly.

spraying beneficial nematodes

When applying nematodes with a sprayer, be sure to remove all screens and filters to allow the nematodes to flow through. Once you mix the nematodes into the water, keep them agitated throughout the application. I continuously shake the sprayer as I am applying them. On a larger scale, submersible pumps are used to keep nematodes in suspension.


After you spray the treatment area, follow up with a a good watering. Beneficial nematodes will have a much higher survival rate if the soil is kept moist. Over the next week, pay closer attention to the soil moisture keeping it from drying out. I try to pick a week where we have a decent amount of rain in the forecast to help.

Once you know the type of nematodes that you need to battle your garden pests, the application couldn’t be easier. They have always made a resounding difference in pest control in our gardens both indoor and out. We have amped it up this year and are looking forward to seeing how many different pests can be thoroughly controlled with these wonderful beneficial nematodes.

Here’s some other great sources for more information on beneficial nematodes:

Beneficial Nematodes for Control of Soil Dwelling Home & Garden Pests – Great for Lawns, Gardens, Yards and Commercial Applications

Beneficial Nematodes Not Effective for Fire Ant Control – University of Florida

Biological Control: Using Beneficial Nematodes – UMass Amherst

Nematodes As Pest Control: Learn About Beneficial Entomopathogenic Nematodes

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