Aphid predators

Most plants in gardens and glasshouses can be attacked by greenfly, blackfly and other aphids, which suck sap, can distort growth and spread plant viruses. Aphids also excrete a sweet liquid called honeydew, which makes plants sticky and allows the growth of sooty moulds. Fortunately, several predatory and parasitic insects found in gardens keep their numbers in check and some of these can be purchased as biological controls for aphids on greenhouse plants. Although the adults of these insects may be familiar to many gardeners, their larvae are often less well known.

2-spot ladybird (Adalia bipunctata). Credit: RHS/Entomology.

Quick facts

Several predatory and parasitic insects found in gardens keep aphid numbers in check
Biological controls for aphids on greenhouse plants can be purchased
Many ladybirds prey on aphids
Lacewing larvae eat aphids and other small insects

What are the main aphid predators?

Ladybirds

There are more than 50 species of ladybird in the UK. They range in size from less than 1mm to over 10mm. They come in a variety of colours including yellow with black spots, brown with cream spots, red with black spots and black with red spots. The number of spots can vary from none to more than 24 and some species are very variable in colour and spot number.

Ladybird larvae are up to 12mm long and are greyish-black with variable amounts of orange-red or white markings. Some species of ladybird larvae have spiny bodies. A majority of species are predatory on aphids and other insects but some feed on mildews and a few species feed on plants. More information on UK ladybirds can be found at the UK ladybird survey.

Hoverfly larvae

Hoverfly larvae are legless maggots with flattened, relatively broad bodies up to 12mm long. They often have semi-transparent bodies so internal structures, such as the gut, can be seen. There are 265 hoverfly species in Britain and just under half of them have larvae that feed on aphids. Adult hoverflies feed on nectar, honeydew and pollen and are useful pollinating insects.

Lacewing larvae  

Lacewing larvae eat aphids and other small insects, which they seize with their curved jaws. They are up to 8mm long with tapered rear ends. Some lacewing larvae camouflage themselves by placing sucked-out aphid skins among the bristles on their upper surface. Adult lacewings have a similar diet to adult hoverflies.

Predatory midge larvae

Predatory  midge larvae, Aphidoletes aphidimyza, are yellowish orange maggots up to 3mm long when fully grown. They insert their mouthparts into the aphid’s body and suck out the contents. When fully fed they go into the soil to pupate and emerge as tiny flies, which feed on honeydew

Parasitic (Parasitoid) wasps (various species)

The adults of several species of small parasitic wasp lay single eggs inside the bodies of young aphids. The egg hatches into a small grub that absorbs nutrients from within the host insect’s body. Eventually the parasite grub kills the aphid, usually by consuming the body contents and pupates inside the dead aphid’s body. By then the parasitized aphid’s body has become whitish brown and has a characteristic inflated appearance and is often called an aphid mummy. The adult parasite emerges through a hole cut in the aphid’s body.

Biological control

Some of these aphid predators can be bought from mail order or some garden centres as biological controls. Biological controls are the use of natural enemies to control pests. This can be done by introducing various predatory or parasitic insects or mites, or nematodes that infect the pest with a fatal bacterial disease. This technique is mainly used in greenhouses, but some biological controls can be used out of doors.

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