Using Beneficial Nematodes to Control Garden Pests

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Introduction

One thing you will hear me preach over and over is the fact that the soil is the single most important aspect to any healthy garden.  Everything starts in the soil.  It's  alive and crawling with billions of organisms, including bacteria, fungi, and insects.   Some of those organisms benefit your plants immensely, some of them are detrimental.  The key to a successful garden is not to eliminate the detrimental organisms all together, but to manage their impact by promoting the beneficial ones. 

Let me introduce to you one of the most important beneficial organisms living in your soil, the nematode.   Nematodes are microscopic non-segmented round worms that flourish in moist soils that contain sufficient food sources in the form of insects, plants, and animals.  That's right, not all nematodes are beneficial to gardening, some of them actually do damage to plant roots.  Luckily there are beneficial ones that will actually parasitize the bad ones.

Nematodes are microscopic soil dwelling round worms

Chances are you probably already have beneficial nematodes living in your garden right now.  They are working hard to devour grubs and overwintering insects as you read this.  Unfortunately they can't keep the levels of those pests down enough to prevent them from doing damage to your garden.  The good news is that you can actually introduce millions of them to your garden with minimal effort! 

Purchasing beneficial nematodes for your garden

Triple threat combo from Arbico Organics

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I sprayed nematodes on Ronin Farm this year for the first time.  I purchased them from Arbico Organics, which is a great company that specializes in all things organic and biological.  I decided to get their triple threat package in order to cover all my bases.  This package comes with three species of beneficial nematodes and is advertised to control over 80 different pests!

​NemAttack, Sc - Armyworm (Pseudaletia unipuncta), Artichoke Plume Moth, Bagworm, Beet Armyworm (Spodoptera exigua (Hubner)), Black Cutworm (Agrotis ipsilon (Hufnagel)), Black Vine Weevil (Otiorhynchus sulcatus), Bluegrass Weevil, Caterpillars, Cockroaches (American, Asian, German), Codling Moth (Cydia pomonella), Corn Earworm, Cotton Bollworm, Cranberry Girdler, Cucumber Beetle, Cutworm (Agrotis, Amathes, Peridroma, Prodenia spp), Fall Armyworm (Spodoptera frugiperda), Flea Larvae, Fly Larvae, Fruit Flies (Drasophylla), Greater Peach Tree Borer (Synanthedon exitiosa), Lesser Peach Tree Borer (Synanthedon pictipes), Large Pine Weevil, Leafminers, Mint Flea Beetle, Mint Root Borer, Mole Crickets, Navel Orangeworm, Strawberry Root Weevil (Otiorhynchus ovatus), Tobacco Budworm, Webworms, Wireworm, Wood Borers
NemAttack, Sf - Beet Armyworm, Black Cutworm, Cabbage Maggot, Codling Moth, Corn Earworm, Cucumber Beetle, Fruit Flies (Drasophylla), Fungus Gnats (Bradysia impatiens), Onion Maggots, Pill Worm, Raspberry Crown Borer, Root Maggots, Sclarids, Shore Flies, Subterranean Termites, Sweet Potato Weevil, Thrips (Franklinothrips sp), Ticks, Tobacco Cutworm
NemaSeek, Hb - Ants (Queen), Asparagus Beetle (Crioceris asparagi; Crioceris duodecimpunctata), Bagworm, Banana Moth, Banana Weevil, Berry Root Weevil, Billbug, Black Vine Weevil, Borers (Iris, Tree, Vine), Carrot Weevil (Listronotus oregonensis), Chafers (European, Masked), Citrus Root Weevil, Colorado Potato Beetle (Leptinotarsa decemlineata), Corn Rootworm, Cranberry Root Weevil, Cucumber Beetle (Spotted) (Diabrotica undecimpunctata howardi), Flea Beetles, Fleas (Adults), Gall Midges, Grape Root Borer, Grubs, Humpbacked Flies, Japanese Beetle (Popillia japonica Newman), Leafminers, May/June Bugs (Phyllophaga sp.), Root Weevils, Scarabs, Sugarcane Stalk Borer, Sweet Potato Weevil, Ticks

They have specific species you can purchase individually as well.  For example, if you are interested in reducing the number of fleas in your lawn you can purchase just the NemAttack for this specific pest.  

Visit Arbico Organics to purchase beneficial nematodes: ​https://www.arbico-organics.com

Applying nematodes to your soil

Applying nematodes is super easy and can be done with a fertilizer injector or backpack sprayer.  I decided to buy a hozon fertilizer injector because I will also use it to apply liquid organic fertilizer to the garden so I can use it for multiple purposes.  ​

Hozon fertilizer injector for applying beneficial nematodes

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I mixed the powder from the triple threat package with water in a 5 gallon bucket.  You don't need to mix it with a specific amount of water, you just need to make sure you cover the specific area based on how much is specified on the package.  I purchased the 10 million count which covers 3,200 sq feet.  Each garden space I was spraying it on was about 1,000 sq ft so I divided the powder into thirds and mixed up three different 5 gallon bucket solutions - one for each garden area I was spraying.  

The hozon fertilizer injector will inject 1 part of your solution with 15 parts of water automatically.  I was able to water each 1,000 sq foot section easily with each 5 gallon bucket of solution without coming close to running out.  This allowed me to get a good soil drench, which is crucial to ensuring the nematodes have a nice moist soil to get established in.  

And that's all there is to it!  Once they are applied to the soil they go to work immediately on parasitizing and devouring your soil pests.  

After three days I dug around in the garden where I sprayed to see if I could find any evidence that they were working. To my surprise I found a white grub that was limp and discolored, which was exactly what I was hoping to find based on my research.  ​

White grub parasitized by beneficial nematodes

Conclusion 

I am very pleased with the results of this experiment.  With a price tag of $80 to cover 3,000 square feet of garden space twice a year, I think it is a great investment when you consider how many different pests this will help to control.  The best part is that this process is not harmful to any beneficial insects including earthworms, lady beetles, or honey bees! (Unlike some organic pesticides)  I will definitely add this to my IPM practices each season.

If you have any questions about the technicalities, or about nematodes in general, please feel free to leave a comment or send me an email.

Happy gardening!  

Written by Corey Wahl
Director of Farm Operations
​Ronin Farm in Bryan, Texas

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