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This video demonstrates how to use beneficial nematodes to manage fungus gnats, shore flies and Western Flower Thrips on crops grown in greenhouses. For more information on beneficial nematodes see: http://extension.umass.edu/floriculture/fact-sheets/biological-control-using-beneficial-nematodes

Beneficial Nematode (Steinernema feltiae)

S. feltiae is especially effective against fungus gnats, thrips and leaf miners. Harmless to the ornamental crops, humans, the environment and other beneficial insects, these nematodes actively seek out fungus gnat larvae by swimming in the thin film of water on soil particles.  They locate hosts by detecting carbon dioxide and other waste products. After locating pest larvae, nematodes invade through natural body openings and inject bacteria into the insect. Bacteria develop within the insect and it dies of septicemia. 

Nematodes, also known as roundworms, can parasitize a wide range of insect pests. There are various species and strains, all with great differences in efficacy. The nematode Steinernema feltiae is used to control thrips. After application, the nematodes actively search for their prey and penetrate them via mouth, anus or respiratory openings.

Target Pest:
 Fungus Gnats, Thrips, Leaf Miners

Release Rates:

For fungus gnat larvae:

Apply 50 million/1,100ft2 (100m2) to 250 million/5,500ft2 (500m2). When fungus gnats are a problem, Exhibitline should be applied every 2-6 weeks.

For best results, treat entire greenhouse or plant inventory as soon as fungus gnats are seen. If fungus gnats are established, it may be 2-3 weeks before the number of adults is noticeably reduced.


For Western Flower thrips:

Soil application - 50 million/2000ft2(200m2) to 250 million/5,500ft2 (1000m2).
Foliage application - 50 million/1,100ft2(400m2) to 250 million/11,000ft2(1,020m2).
Un-rooted cutting or rooted cutting dip - 50 million/13 gallons of dipping solution.

Lifespan:

Development from egg to adult takes from 7-9 days at 70°F, to 3 days at 85°F. At 78°F, a fourfold increase in numbers can occur within 4 days. In the field, under optimum conditions, populations can increase from 10 predators per 100 leaves, to 200-500 predators per 100 leaves in just 2 weeks.

Adult females lay 1-5 eggs per day, for a total of 26-60 eggs over their lifetime (which could be between 14-62 days). The eggs hatch in 2-3 days, which are oval in shape and twice the size of the two-spotted mite eggs. Newly hatched predators do not eat, but later stages and adults feed on all stages of prey. Female Fallacis can eat 2-16 spider mites per day.

Adult females enter diapause in response to the short days in the fall (less than 14 hours of daylight). They stop reproducing and move into sheltered areas, such as under bark or ground cover. They do not enter diapause in greenhouses or interior plantscapes if the temperature is 64°F or above.

Strategic Considerations:

It is best to release all Beneficial Nematodes the same day as received. If this is not possible, you can store these in a household refrigerator for a week or so, two weeks max. Release in early morning, late afternoon, or when temperatures are not extremely hot. Cloudy days are perfect all day. Moisten soil prior to application & lightly water again after applying Nematodes Beneficial Nematodes may be mixed and used in a watering can or hose-end sprayer. Place the entire sponge in a clean bowl or bucket. Pour at least one quart of lukewarm water over the sponge and repeatedly squeeze for a few minutes to get the Nematodes out of the sponge and into the water.

Repeat this process with a second bowl or bucket of clean water. (Once nematodes are removed from the sponge, you must disperse them within 1 hour.) Discard the sponge and pour both containers of water into a sprayer or watering can. Some nematodes will be on the interior surface of the bag. Rinse out the bag with water and pour into the sprayer or watering can. At this stage, you should have the amount of nematodes indicated on the open bags suspended in about two quarts of water. Add clean water to dilute the suspension and to make up the volume that your spray or application apparatus requires for application of said coverage area.

Selected References

UC Pest Management Guidelines

Biological Control of Fungus Gnats with Beneficial Nematodes

UMASS - Biological Control: Using Beneficial Nematodes

Incorporating nematodes into an insect control program