University of Maryland Extension


Back to Parasitoids

closeup of beneficial nematode
Beneficial nematode

white grub parasitized by nematodes
Beetle grub infested with nematodes

Parasitic nematodes: are tiny, parasitic worms that are not harmful to humans, animals or plants. These occur naturally, mainly in soils, and can be purchased to control clear-wing borers and cutworms. There are two types available- Steinernema (Sc) and Heterorhabditis (Hb). Sc nematodes work on insects that feed near the soil surface or inside plants while Hb nematodes can move through the soil profile to attack certain beetle grubs.

Nematodes require a moist environment to survive and to move about. Efforts to use them on plant foliage have been largely unsuccessful. lt is now recognized that their effectiveness is greatest in soil or other moist habitats such as cranberry bogs. However, they have been useful in controlling several species of wood-boring caterpillars in alder, sycamore, dogwood, and cherry laurel. Good control can be achieved against certain curculionid grubs, such as black vine weevil, and strawberry root weevil in containerized nursery stock and nematodes have become commercially accepted for this use. Because nematodes depend on water-filled spaces between soil particles to move and find hosts, their effectiveness is reduced in dry soils and in clay soils (which lack adequate pore spaces). They function best in moist loam soils, rich in organic matter.

Follow package directions for appropriate storage and application techniques.

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