Predators are organisms which feed on a number of their natural prey. There are several advantages in using predators. They often attack different life stages of the pest, and even different pest species.
Many predators are also able to supplement their diet by feeding on alternative food sources, such as nectar, pollen and fungi. They are often voracious feeders and more robust than parasites.
The disadvantage of using predators is that they usually require higher populations of their prey to work effectively and once they have ‘cleaned them up’ may disappear from the scene.
Predatory Beetles - eg: ladybirds, carabid beetles
Predatory Bugs - eg. assassin bugs, damsel bugs, predatory shield bugs
Other predators - eg. lacewings, spiders, hover fly, ants...
Parasites - more correctly called ‘parasitoids’ - are usually tiny wasps but are can also be parasitoid flies. They deposit an egg into or onto the pest, usually at a critical life stage. The larva that hatches ultimately consumes and kills the pest. Each parasitoid completes its entire development on an individual host. Sometimes many parasitoids may emerge from one pest.
The advantages of using parasitoids are that they are usually well adapted to their natural host and are very good at finding them even when densities of the host are relatively low.
The disadvantage of using parasitoids is that they are mostly very host-specific and often will attack only one or a few species of pest. They are also generally more delicate than predators and hence more vulnerable to pesticides.
Because parasitoids spend most of their life cycle developing within their prey, they are less visible than predators, and their performance may be underestimated as a result.
Entomopathogenic nematodes are often called pathogens but are technically parasitoids as theywill kill their host in the process of completing their life cycle.
Parasitoids - Trichogramma, Anastatus, Trissolcus, Cotesia, Diadegma, Tachanid flies...
Predators: Assassin bugs (20 mm)are commonly found in tree crops and are capable of killing large caterpillars and giving a nasty bite.
Parasitoids: Cotesia wasps (4 mm long) a parasitoid of cabbage white butterfly larva and army worms are often found in vegetable crops having emerged from their characteristic yellow or white bundles of cocoons.
Hover fly adult - the larva of hover flies predate on mites and aphids.