Beneficial Insects - Predatory Nematodes Notes on Nematodes
- Predatory nematodes are naturally occurring microscopic worms that attack white grubs and other soil larvae. Nematodes are typically 1/500 of an inch in diameter and 1/20 of an inch in length.
- Nematodes are all natural living organisms and are harmless to humans, pets and earthworms.
- The life cycle of nematodes consists of eggs, four larval stages and the adult. The third larval stage of the nematode is when they are most effective at controlling target insects.
- They search out susceptible hosts and enter them through the mouth, breathing holes or the anus.
- Once inside, the host is infected with a symbiotic bacterium which causes the death of the host. Reproduction inside the dead insect releases a new generation of nematodes which disperse in search of further prey.
- They are best used as a preventative application applied to newly hatched larvae. This means that the best time to apply the nematodes to white grubs is in the fall.
- The nematodes may not control all the grubs in the soil, but will reduce the grub population and thereby reduce any potential lawn damage.
- Nematodes need moisture to live and thrive. Soil temperatures should be between 12-20 degrees Celsius.
- Soil aeration prior to an application will facilitate the movement of the grubs into the root zone.
- A heavy watering prior to or just after the application is necessary to keep the nematodes alive. This will moisten the soil and the thatch.
- Water the nematodes into the soil as soon as possible. This carries the nematodes off the grass into the soil where the grubs live. Too much sunlight can be harmful to the nematodes.
- Water well for 3 days after the application to ensure adequate moisture levels and allow the nematodes to move to their grub targets.
Grubs will take some time to be fully dead after a nematode treatment. see Dying Grubs Infected by Nematodes