Integrated Pest Management Guide

BENEFICIAL NEMATODES

Infective juvenile nematodes enter the body of the insect via body openings such as the anus, mouth parts, or breathing holes, and release bacteria. The bacteria colonize the insect, which usually dies within 48 hours. The nematodes then feed on the bacterial cells and the degrading host tissue. Nematodes mature, mate, and may produce up to three generations in the same host. Most nematodes effective in pest control belong to two genera: Steinernema and Heterorhabditis. Commercially raised nematodes possess a number of attributes relevant to the control of weevils and cranberry girdlers. Steinernema carpocapsae is a passive sit-and-wait or "ambush" forager, remaining near the soil surface and attaching to passing hosts. Consequently, S. carpocapsae tends to be most effective when applied against highly mobile surface-adapted insects. Heterorhabditis species penetrate more deeply into the soil and use an active "cruiser" strategy to locate and infect sedentary insects. S. carpocapsae is recommended for weevils and cranberry girdlers while H. bacteriophora is mostly recommended for cranberry girdlers. Both species can be applied by chemigation or boom sprayer. Nematodes are living organisms. To be effective as biological control agents they have to be kept alive, applied under the right conditions and handled properly. Nematodes are very sensitive to certain environmental factors and are quite intolerant of ultraviolet radiation, desiccation and temperatures below 14º C (54º F) and above 30º C (86º F).

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