Beneficial nematodes are microscopic roundworms used in gardening and agriculture as a natural way to manage various insect pests in soil without relying on synthetic pesticides. This guide covers how to choose the correct species, where to purchase them, and the steps for successful application to ensure pest control success.
Choosing the Right Species for Pest Control
Selecting the appropriate nematode species is essential for effective pest management. Different species of entomopathogenic nematodes (EPNs) target distinct pests and thrive in specific soil conditions and temperatures. Matching the nematode to the target pest ensures successful control.
Steinernema feltiae is effective against pests near the soil surface or in cooler environments, such as fungus gnat larvae, flea larvae, and cutworms. This species remains active down to about 50°F (10°C), making it suitable for early spring, late fall, or indoor houseplant applications. It is an active-hunting or “cruising” forager, moving through the soil to seek out its prey.
For warmer soils and more deeply buried pests, Heterorhabditis bacteriophora is the preferred choice, performing best when soil temperatures are above 68°F (20°C). This species is highly effective against major turf and garden pests like Japanese beetle grubs, European chafer grubs, and root weevils. H. bacteriophora also employs a cruising strategy, actively burrowing to seek out hosts deeper in the soil.
A third common species, Steinernema carpocapsae, is known as an “ambush” forager, waiting near the soil surface for mobile insects to pass by. This strategy makes it ideal for controlling surface-dwelling pests such as ticks, crickets, mole crickets, and certain caterpillars. The optimal temperature range for S. carpocapsae is generally between 72°F and 82°F (22°C–28°C), making it a summer-use product.
Sourcing and Purchasing Options
Purchasing live biological control agents requires careful consideration of the vendor to ensure the product arrives viable. Reputable sources include online biological control suppliers, specialized garden centers, and general big-box stores.
Online suppliers often offer the largest selection of species and package sizes, frequently selling directly from the producer. Buying from these specialized vendors provides a higher assurance of product freshness since they are accustomed to shipping live organisms. However, shipping times and transit delays can compromise the nematodes’ viability before arrival.
Specialized garden centers and local nurseries are an excellent option because staff are typically educated on proper storage and application. These centers usually store the product under correct refrigeration, minimizing the risk of heat or improper handling. Although selection may be smaller than online vendors, the quality and freshness are often reliable, and staff can provide localized advice.
General big-box stores are convenient but carry a higher risk of the product being compromised due to less consistent storage conditions. If the product is left on a shelf or exposed to fluctuating temperatures, the organisms may be dead or significantly weakened upon purchase. If buying from a general retailer, check the packaging date and ensure the product has been kept under refrigeration.
Immediate Handling and Storage
Nematodes are living organisms, and their viability depends entirely on immediate and correct handling upon delivery or purchase. Inspect the shipping package immediately for any signs of damage or excessive heat exposure, as high temperatures quickly kill the organisms.
The nematodes must be refrigerated immediately upon arrival, ideally kept at a constant temperature between 38°F and 42°F (3°C–6°C). They should never be frozen or stored near the freezer compartment or in a frequently opened refrigerator. Most commercially packaged nematodes have a short shelf life, often only two to four weeks, and should be used as soon as possible.
Nematodes are typically packaged in a moist, inert carrier material like a sponge, clay powder, or gel. Keep the package unopened in the refrigerator until application to maintain coolness and prevent desiccation. Direct sunlight is highly detrimental because UV light rapidly kills the organisms.
Successful Application Techniques
Successful application depends heavily on environmental conditions, especially moisture and temperature, to ensure nematode survival and movement. The soil must be pre-moistened before application, as nematodes require a film of water to move through the soil to find their insect hosts.
Application should be timed for early morning, late evening, or a cloudy day to prevent exposure to direct sunlight and UV radiation. Soil temperatures should generally be between 55°F and 85°F (13°C–29°C), depending on the species, since temperatures outside this range reduce effectiveness.
Mix the nematodes with cool, clean water in a bucket or container, avoiding highly chlorinated or hot sources. Application can use a watering can, hose-end sprayer, or pump sprayer, but all fine mesh filters must be removed to prevent clogging. Continuous agitation of the solution is necessary during application because the nematodes quickly settle to the bottom.
Following application, water the treated area lightly but thoroughly to wash the nematodes off foliage and into the top layers of the soil. Maintaining consistently moist soil for at least three to seven days post-application allows the nematodes to establish themselves and actively seek out host insects.