Beneficial nematodes represent a biological method of pest management, using microscopic, worm-like organisms to target and control various soil-dwelling insects. These organisms are applied directly to the soil, where they actively seek out and parasitize pests like fungus gnat larvae, grubs, and weevils. A standard watering can offers an effective and precise tool for delivering these live biological controls to small garden areas or container plants. Success with this method relies on careful preparation and a specific application technique to ensure the nematodes remain viable and are evenly distributed across the treatment area.
Pre-Application Setup and Handling
Successful application begins with properly handling the live organisms before mixing them with water. Upon arrival, store packaged nematodes immediately in a refrigerator between 38–42°F, as they are sensitive to heat and should never be frozen. Before application, prepare your watering can by removing any fine rose or filter, since the microscopic organisms can become trapped or clogged by a mesh finer than 50-mesh.
The water used must be clean and cool, ideally between 59–69°F, to maintain viability. Avoid tap water high in chlorine; if used, let it sit for a day to allow the chlorine to dissipate. If nematodes are packaged in a carrier material like a sponge, submerge and gently squeeze the sponge multiple times to release the organisms into the liquid.
Mixing Ratios and Suspension
Creating the solution requires careful attention to dilution and suspension to ensure the organisms are not damaged or allowed to settle. A starting guideline is to mix about one teaspoon of the material per gallon of water, but always consult the product label for specific instructions. First, mix the entire contents of the package into a small volume of water to create a concentrated stock solution, ensuring all organisms are released from the carrier material.
Stir this stock solution vigorously to dissolve any clay or powder and fully release the nematodes. Once ready, dilute the concentrate into the full volume of water required to cover the target area. Apply the mixture promptly, ideally within one to two hours of activation, because nematodes settle quickly and can suffocate if left too long at the bottom of the can.
Effective Application Technique
Applying the solution demands continuous movement and agitation to prevent the organisms from sinking. Since nematodes are denser than water, they quickly settle to the bottom of the watering can, causing uneven distribution. To counteract this, constantly stir or swirl the water inside the can using a stick or your hand as you walk and pour.
Focus the application on thoroughly drenching the soil surface, ensuring the solution reaches the root zone where most soil-dwelling pests reside. Aim for even coverage over the entire designated area. Do not worry if every inch is not covered, as the nematodes are capable of moving through the soil to find prey.
Post-Application Steps
Immediate follow-up actions ensure the nematodes successfully migrate into the soil. As soon as the can is empty, thoroughly rinse it with water to prevent any remaining organisms from drying out. The most crucial step is to “water in” the treated area immediately after application.
This follow-up watering should be light but sufficient to wash any nematodes that landed on foliage down into the soil, helping them penetrate the upper layer. Maintaining soil moisture for the next three to five days is important, as this damp environment allows the nematodes to move and hunt effectively. Keep the soil moist, but never waterlogged, for up to two weeks after application to maximize the longevity and effectiveness of the biological control.