Species

Insect-parasitic nematodes (Nematoda) exist as three different beneficial species- Heterorhabditis bacteriophora, Steinernema carpocapsae, and S. feltiae.

Identification

Life Cycle

Parasitic nematodes begin their lives as juveniles, scouring the soil for insects to infiltrate and use as a host for development. Once inside their host, the nematodes release a bacterium which causes the host to die within 48 hours. The nematodes then feed on the bacterium and decaying insect tissue. This time period, which can last up to five days, is the developmental stage. At the end of this stage the nematodes reach maturity and reproduce, releasing eggs inside the body of the host. The eggs hatch and develop into juvenile nematodes which exit back into the soil when the host insect cracks open, beginning the cycle over again.

Prey

Different species of parasitic N\nematodes attack different pests. Keep this is mind when choosing which nematode would best serve your garden.

Function

Insect-parasitic nematodes feed on insects found in moist, dark areas such as soils, lawns, and tree trunks. They attack other insects, also known as hosts, by latching on to and then penetrating the insect's body through one of its openings, such as the mouth or anus. Once inside, the nematodes release a bacterium which causes the host insect to die within several days. The nematodes then feed on the decaying insect.

Different species of parasitic nematodes use different methods of attack, explaining why certain species of nematodes are adept at controlling different pests. The Steinernema carpocapsae waits for its prey near the soil surface and then attacks when it comes into range. Heterorhabditis bacteriophora is the opposite, cruising around at deeper soil levels and actually seeking out its prey.

Commercial Availability

Parasitic nematodes are widely available for purchase through a number of online distributors. They are also available at local nurseries during the growing season when soil temperatures are likely to be appropriate for dispersing them.

Handling and Use

Be sure to follow the directions for storage and use provided by your distributor as certain species have unique handling instructions.

Some common guidelines to keep in mind:

• Nematodes are vulnerable to extreme temperatures. Refrain from exposing them to freezing temperatures while storing them in the refrigerator and never release them on days with extreme heat.
• Most nematodes can tolerate soil temperature of 55 degrees F so be sure to test soil temperature before releasing.
• Release only in the evening to avoid nematodes being instantly killed by exposure to direct sunlight.
• Since nematodes like moist environments, water the soil where the nematodes will be working before their release.
• Once released spray off the leaves of all plants to ensure that the nematodes are all in the soil.
• Keep the soil moist but not overly saturated to prevent it from drying and incapacitating the nematodes.
  

Cultivation Techniques

Nematodes naturally occur in gardens but due to their vulnerability to temperature, sunlight, and other pests they are difficult to conserve. To attract native populations or develop introduced populations keep soil moist at all times and make sure that proper foliage exists to keep soil temperatures from over heating.

References

Cranshaw, W.S. and R. Zimmerman. "Insect Parasitic Nematodes." 2008.
Colorado State University Extension. 23 Sept. 2008.
< http://www.liu.edu/cwis/cwp/Library/workshop/citmla.htm>.

Flint, Mary Louise, and Steve H. Dreistadt. +Natural Enemies Handbook: The Illustrated Guide to
Biological Pest Control+. Berkeley: UC Division of Agriculture and Natural Resources and the University of California Press, 1998.

Grewal, Dr. Partwinder. "Insect Parasitic Nematodes." 2008. Department of Entomology,
Ohio State University. 23 Sept. 2008.
< http://www.oardc.ohio-state.edu/nematodes/default.htm>.