Biological Control is a method of controlling pests using other living organisms- it relies on predation, parasitism, herbivory (for weed) or other natural agents, avoiding using synthesised chemicals that may damage the environment. It usually involves an active human management role, but this varies between types. The 3 types are:
Classical Biological Control: Introduction of a natural enemy to an area in order to bring an introduced pest under control. Enemies are usually imported from pests’ origin and already predate/parasitise the best there, but New Association Biological Control attempts to find an enemy that is attacking taxonomically or ecologically related species.
Augmentative Biological Control: Periodic introduction of a natural enemy to an area in order to augment the existing population to allow greater control.
Biological Control by Conservation: Providing key resources for natural enemies and reducing pesticide impacts (pollen, nectar, nesting sites). Habitat manipulation methods include mulch, conservation tillage, intercropping, field borders and hedgerow planting.
The bio control agents can vary according to the target, and they usually either eat the pest insect (predatory) or lay eggs on or inside the pest insect’s body to use as food for the developing larvae, and is eventually killed (parasitism). Some well known examples of enemies (and their target pest in brackets) are:
Predators: ladybirds (aphids, whitefly, scales, mealybugs), hoverfly larvae (greenfly, mites), dragonflies (mosquito larvae), pirate bugs (thrips), rove and ground beetles, predatory spider mites.
Parasitoids: Ichneumonid wasps (lepidoptera larvae), braconid wasps (greenfly, small white larvae), chalcid wasps (greenfly, whitefly, scales, tortrix, small white larvae), tachinid flies (adult and larval beetles, true bugs)