Beneficials
A living creature that helps crops, above all by keeping pests in check: predators and parasitoids, their natural enemies.
Explanation
Ladybird, lacewing, ground beetle, ichneumon wasp: “beneficial” names a role, not a group of species. In crop protection, beneficials are the natural enemies of pests: predators, which hunt or trap their prey, and parasites or parasitoids, which complete their development at the expense of pests (Ephytia, INRAE). Permagora files pollinators separately, and counts a few soil allies such as the earthworm among beneficials. In the garden, the key is to welcome them: offering them food and shelter is conservation biological control.
Refined definition
A beneficial keeps the population of a crop enemy (insect, mite, slug) in check in two main ways. The predator hunts prey to feed itself or its larvae. The parasitoid lives on or inside the body of its host, from which it draws its food during part of its development, which leads to the host's death (Ephytia, INRAE). Its role is to regulate, not to eradicate: it needs its prey in order to stay.
Key points
Predators and parasitoids of the garden
PREDATORS: the ladybird, adult and larva alike, and the lacewing larva eat aphids; the ground beetle hunts at night, on the ground, slugs, snails, eggs and fallen caterpillars; the small Orius bug attacks thrips and mites. PARASITOIDS: the female ichneumon wasp lays in or on a caterpillar, larva or pupa of a pest, which her larva devours from the inside; the tiny trichogramma lays in the eggs of pest moths and butterflies. The fact sheets for these beneficials give their sources.
Food and shelter
Landis, Wratten & Gurr (2000), in the Annual Review of Entomology, describe how to manage habitat to conserve these natural enemies: provide food for adults, alternative prey or hosts, and shelter from adverse conditions. In the garden, that means flowers from spring to autumn, hedges, strips of grass left tall, piles of stones or wood.
Keeping some prey
To last, a beneficial must find something to live on, even when the target pest is scarce. This is why Landis and colleagues count alternative prey and hosts among the resources to offer; banker plants are a garden application of it.
Watch out for
- • “Beneficial” and “pest” describe a role, not a nature: the earwig, useful against aphids and mites, can also nibble flowers, lettuces and ripe fruit when it swarms.
- • Some beneficials can be bought, mostly for greenhouses (the Orius bug, for example). In the open garden, whether they stay depends on the same resources as for wild beneficials: food, prey, shelter.
Sources
- Landis, D.A., Wratten, S.D. & Gurr, G.M. (2000). Habitat management to conserve natural enemies of arthropod pests in agriculture. Annual Review of Entomology, 45, 175-201.
- INRAE, Ephytia (ephytia.inrae.fr)