Beneficial nematodes are an easy way to begin a biocontrol program in greenhouses. Beneficial nematodes (Steinernema feltia) are best applied as a media drench to target the fungus gnat larvae. Treat as soon as possible (2 to 3 days) after sticking cuttings, planting plugs or starting seeds.
Storage and Viability
If possible, apply beneficial nematodes immediately after receiving them. If you must store the nematodes, store them in a refrigerator at a constant 40° F. Avoid storing them in a refrigerator that gets opened frequently. It is best to purchase a dedicated refrigerator just for biocontrols so you have more even temperatures.
After taking them from storage, allow the nematodes to warm a little at room temperature (about 10 minutes) to "wake up" before mixing them in the tank solution to avoid drastic changes in temperature.
Check their viability before application. To do this, place a small amount of the product in a small container. Add 1 or 2 drops of room temperature water; wait a few minutes and look for actively moving or swimming nematodes. Use a dark black background and a hand lens to see the small (0.6 mm or 0.02 inches in length) nematodes. Or shine a flashlight on them. Live nematodes actively move. Dead nematodes are usually straight, like an arrow.
Nematodes are very sensitive to UV light and desiccation. Therefore, apply nematodes in the evening or at dusk or on a cloudy, overcast day.
Nematodes can be applied using a sprayer (remove screens and filters), injector, hose end sprayer or even a watering can in very small operations. Remove any screens and filters to prevent clogging. The hose nozzle should have large openings so the nematodes can move freely through this opening. If using a sprayer, keep spray pressure below 300 psi.
Media temperatures should be above 50° F but avoid applying when soil temperatures are above 80°F. Optimum media temperatures are between 60-70°F. (Use a soil thermometer to monitor temperatures).
Although nematodes are applied in water, they are not aquatic animals so they need extra care while in stock and tank solutions. Adequate aeration of the nematode suspension during application is important. This can be done using a small battery powered submersible pump or even mechanically with a stirrer to keep the solution agitated. A small pump will also keep them from settling on the bottom of the stock solution container, which they tend to do. The suspension in the spray tank should be kept cool and applied as soon as possible after mixing. This is especially important during the warmer months. The longer they are kept before spraying and the warmer the tank water, the more quickly their energy reserves are used up. Weaker nematodes are less robust during and after application, and less able to search for and infect a susceptible host.
Water the growing media before and after application. (Nematodes need moisture for movement). But, avoid over watering, so they are not washed out of the container.
Repeated applications are often needed. Reapply in 2 to 4 weeks under moderate to heavy infestations. For longer term crops, apply at the beginning and at mid-crop.
Tina Smith, UMass Extension and Leanne Pundt, UConn Extension
Pesticide Compatibility Charts and Data bases
Koppert, Inc., (see side effects on left) – this brings you to their data base where you can input “Steinernema feltiae” under “latin name” and then plug in the product you plan to use.
Biobest, Check under 'Side Effects' – easy to use data base
Bioline compatibility chart from Syngenta - see Exhibitline (Steinernema feltiae)