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Steinernema and Heterorhabditis nematodes provide the best control when environmental conditions keep them healthy.   These guidelines pertain to using nematodes under most situations, but check out our FactSheets for using insect parasitic nematodes under special conditions.  For an excellent overview, send for our free companion video, Insect Parasitic Nematodes:  "Tools for Pest Management".

General Guidelines

Target Pests
Weevils      Billbugs Black vine weevil Strawberry root weevil Citrus weevils Carrot weevils
Caterpillars Cutworms Army worms Sod webworms Artichoke plume moth Clear wing moth Iris borer
Flies Fungus gnats Sciarid larvae
Beetles Flea beetles
Mole crickets
Flea (larvae)

Insect parasitic nematodes, as with most biological control agents, are living organisms that require a few extra steps to ensure that they remain healthy and able to effectively contact their host insect. Our FactSheets provide specific information on pests in turf, strawberries, cranberries, and pests that might be found in the backyard garden. Check with suppliers and extension agents to see if your pest concern requires modification of these steps which are critical to achieving the best pest control.

Choosing the right nematode is critical.  Nematodes are formulated and applied as infective juveniles - the environmentally-tolerant, free-living stage that attacks the insect. There are several species and strains on the market today that are specialized for particular host insects, and their temperature tolerance and behavior differ depending on the species. It is critical to choose the right species for the job. Check our Biology/Ecology page to review these nematode types. Briefly, Steinernema carpocapsae uses an "ambush" strategy as they wait for an insect host to move by, and therefore work well against pests that are moving around on the soil surface.

Heterorhabditids do well against soil pests that are not as mobile because these nematodes are "cruisers", they actively search for hosts deeper in the soil profile.

Proper storage and handling is essential to nematode health.  Always follow the package instructions for the best method of mixing nematodes. Formulations vary depending on the species and target insect. They can include gels, dry granules, clay, vermiculite, and water-filled sponges. No matter which formulation you buy, nematodes should be used as soon as possible after receiving them from the supplier because the length of time they were stored prior to shipment is usually unknown. Steinernema species can be stored in the refrigerator up to a month (not the freezer) before they are mixed with water, but once the nematodes are diluted in water, they cannot be stored. Also, nematodes shouldn’t be stored in hot vehicles, or left in spray tanks for long periods of time.

Nematodes need moisture in the soil for movement (if the soil is too dry or compact, they may not able to search out hosts) and high humidity if they are used against foliage pests. Watering the insect-infested area before and after applying nematodes keeps the soil moist and helps move them deeper into the soil. Care should be taken not to soak the area because nematodes in too much water cannot infect.

Exposure to UV light or very high temperatures can kill nematodes. Apply nematodes in the early evening when soil temps are lower and UV incidence is lower as well (cloudy or rainy days are good too). Nematodes function best with soil temperatures between 60Fº and 93Fº.

There is no need for masks or specialized safety equipment. Insect parasitic nematodes are safe for plants and animals (worms, birds, pets, children). They are exempt from EPA registration and can be used legally everywhere with few exceptions (not yet legal in Hawaii). Because they leave no residues, application can be made anytime before a harvest and there is no re-entry time after application.

Fertilizers should be avoided roughly 2 weeks prior to and after nematode application, because they may be adversely affected by high nitrogen content.

Some pesticides work well with nematodes when their mutual exposure is limited while other pesticides may kill nematodes. Check labels or specific fact sheets to find out. Some chemicals to avoid are bendiocarb, chlorpyrifos, ethoprop, and isazophos. Fungicides to avoid are anilazine, dimethyl benzyl, ammonium chloride, fenarimol, and mercurous chloride. The herbicides, 2,4-D and trichlopyr and nematicide, fenamiphos, should be avoided as well.

Choose a reputable supplier. A reputable supplier will probably sell different species and provide information on pests and application

Assessing efficacy may require time.  Results may not be noticeable for 2 - 3 weeks unless it is a soil pest that would not emerge until the next season (spring). Infected insects turn a brownish-yellow when killed by Steinernema and a brick-red to purple when killed by Heterorhabditis.

Left: infected by Steinernema Right:by  Heterorhabditis

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