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Biological control of sciarid flies - Steinernema feltiae

Sciarid flies can cause damage to cuttings and other young growing plant material. They are key pest in the cultivation of mushrooms. Sciarid flies cause indirect damage by spreading mites, viruses and fungi. Direct damage is the result of the larvae chewing on the roots. Luckily the gnats can be combatted by entomopathogenic nematodes, also known as roundworms. There are various species and strains, all with great differences in efficacy. The nematode Steinernema feltiae is used to control sciarid flies. After application, the nematodes actively search for their prey and penetrate them via mouth, anus or respiratory openings. Once inside, the nematodes feed on the contents of the prey, excreting specific bacteria as they do so. These bacteria spread inside the insect and convert host tissue into products that the nematodes can easily ingest. The insect dies within a few days. Affected insects turn yellow to light brown and become slimy or dehydrated. The growth of the population of nematodes within the host depends on two factors: the number of infectious nematodes that penetrate the host insect, and the size of the host. Female nematodes can lay up to 200 eggs. The female lays her eggs inside the host or when there is insufficient food, the eggs will develop inside the female nematode. From the eggs that remain viable hatch larvae that rapidly develop. Several thousand nematodes can eventually leave the host. They immediately start searching for new prey.

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