''Aphelinus mali'' is a

parasitoid wasp Parasitoid wasps are a large group of hymenopteran Superfamily (zoology), superfamilies, with all but the wood wasps (Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, ...

that exploits the woolly apple aphid (''

Eriosoma lanigerum ''Eriosoma lanigerum'', the woolly apple aphid, woolly aphid or American blight, is an aphid in the superfamily Aphidoidea in the order Hemiptera. It is a true bug and sucks sap from plants. Description The adults of ''Eriosoma lanigerum'' are ...

''), a pest of apple trees. It is native to the northeastern United States but has been introduced to other parts of the world as a

biological pest control Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or ot ...

agent.

Description

The adult ''A. mali'' is a tiny black wasp slightly smaller than its woolly aphid

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County * Host Island, in the Wilhelm Archipelago, Antarctica People * ...

. Its transparent membranous wings are longer than its abdomen and fold flat along its back. Although it can fly, it prefers to walk and jump, and often conceals itself under leaves. The larvae and pupae remain hidden inside the host; the larvae are yellow with red eyes, and the pupae are black.

Distribution

This parasitoid is a parasite of aphids, particularly woolly aphids and is native to the northeastern parts of the United States. It was introduced in 1928 to the orchards of the

Pacific Northwest The Pacific Northwest (PNW; ) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common ...

in the region of Hood River and spread naturally. It has since been introduced to many other parts of the world with the aim of keeping aphids under control.

Life cycle

The adult female ''A. mali'' emerges from

diapause In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press It ...

in the spring. It inserts its

ovipositor The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typica ...

into the underside of a woolly aphid and lays an egg, which hatches in about three days. The adult may feed on any fluid that oozes from the puncture wound. The larva takes ten to twelve days to develop before pupating inside the body of its host. When ready to emerge, the adult chews its way out through the upper surface of the aphid, leaving a neat round hole. The whole life cycle takes 20 to 25 days and there may be six or seven generations during the season. In the fall, larvae and pupae enter diapause and overwinter in the blackened mummified bodies of their hosts.

Use in pest control

Introduced from its native region to other apple growing areas, ''A. mali'' was one of the earliest examples of controlling pests biologically. It works best in conjunction with other generalist predators such as

lady beetle Coccinellidae () is a widespread family (biology), family of small beetles. They are commonly known as ladybugs in North America and ladybirds in the United Kingdom; "lady" refers to Mary, mother of Jesus, mother Mary. Entomologists use the ...

lacewings The insect order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order consists of some 6,000 species. Neuroptera is grouped together with the Megaloptera ( alderflies, fishflies, ...

, the larvae of

hoverflies Hoverflies, also called flower flies or syrphids, make up the insect family (biology), family Syrphidae. As their common name suggests, they are often seen Hover (behaviour), hovering or nectaring at flowers; the adults of many species feed main ...

and the plant bug ''

Deraeocoris brevis ''Deraeocoris brevis'' is a species of predatory plant bug in the family Miridae. It is native to North America where it feeds on plant pests in apple and pear orchards. Description ''D. brevis'' is a hemimetabolous insect, undergoing incomplete ...

'', and is negatively impacted by the use of chemical pesticides.

References

{{Authority control Aphelinidae Insects described in 1851 Taxa named by Samuel Stehman Haldeman Hymenoptera of North America Biological pest control wasps