Hosts or Prey
Ash whitefly and nymphs of various other whitefly species
Identification
This wasp's presence is most recognizable by the change in appearance of parasitized hosts. Unparasitized whiteflies of most species are translucent to whitish. Parasitized whiteflies turn blackish or brown and develop a crusty, puffy (mummified) covering. When E. inaron emerges from a host it chews a round exit hole in a host covering that remains discolored dark and contains dark excrement pellets (meconium) of the wasp. When an adult whitefly emerges from its fourth instar (pupal) covering it leaves a ragged slit and an empty covering that is generally transparent to whitish.
The adult E. inaron is a wasp about 1/40 inch (0.6 mm) long. It has a blackish to dark brown head and thorax and clear wings. The abdomen of females is yellow and that of males is black.
Eggs, larvae, and pupae occur hidden inside whitefly nymphs and pupae. The oblong eggs and maggotlike larvae are pale yellow to whitish. Pupae are initially pale colored then as they age darken and develop distinct appendages folded against the body.
Life Cycle
Encarsia inaron develops through 4 life stages: egg, larva, pupa, and adult. The adult female lives about 3 weeks when temperatures average 77ºF. The male lifespan is somewhat shorter. Adults feed on honeydew and nectar and the adult females feed on the hemolymph (blood) of whiteflies. The female wasp punctures whitefly nymphs with her ovipositor then consumes the exuding body contents. When whiteflies are host fed upon they die and are not used for parasitoid egg laying.
During her life each adult female on average lays about 160 eggs. The mated adult female wasp oviposits in second through fourth instar whiteflies of several species including the ash whitefly. She parasitizes about 8 whiteflies per day and host feeds on several more.
Development time from an egg to a reproductive adult is about 3 weeks when temperatures average 80ºF. Encarsia inaron has multiple generations per year.
Habitat
Ash whitefly was inadvertently introduced into California in 1988 and it quickly spread throughout much of the state. The whitefly infested at least 55 species of plants. Hosts became heavily infested by nymphs that excrete prolific honeydew that fouls plants and surfaces underneath. Heavily infested plants prematurely dropped their leaves. During warm weather enormous numbers of flying adults annoyed people.
This pest's introduction prompted the California Department of Food and Agriculture and University of California to conduct foreign exploration for natural enemies. The parasitic wasp E. inaron (then named E. partenopea) and a small lady beetle (ladybug or ladybird beetle), Clitostethus arcuatus, were introduced. These natural enemies spread everywhere the whitefly occurs.
Encarsia inaron especially has reduced the abundance of ash whitefly to innocuous levels in most situations. The economic benefit of this classical biological control program that improves plant quality and avoids the costs of ongoing management is over $200,000,000 per year forever.
Species
At least 30 species of Encarsia occur in California. Many of these parasitize multiple species of scale insects, whiteflies, or other plant-sucking insects formerly called Homoptera. For example E. formosa is a naturally occurring parasitoid that is commercially reared and sold to control greenhouse whitely infesting greenhouse crops. Encarsia inaron parasitizes nymphs of at least 29 species of whiteflies.
More Information
- Ash Whitefly, Center for Invasive Species Research, UC Riverside
- Ash Whitefly (Homoptera: Aleyrodidae) Overwintering and Biological Control by Encarsia inaron (Hymenoptera: Aphelinidae) in Northern California, UC Integrated Pest Management Program, Biological Control
- Biology of Siphoninus phillyreae (Haliday) (Homoptera: Aleyrodidae) and its Relationship to Temperature, UC Riverside, Environmental Entomology
- Classical Biological Control of Ash Whitefly: Factors Contributing to its Success in California, California Department of Food & Agriculture, Biocontrol
- Encarsia inaron (Hymenoptera: Aphelinidae), Cornell University
- Establishment of the Ash Whitefly Parasitoid Encarsia inaron (Walker) and its Economic Benefit to Ornamental Street Trees in California, Biological Control
- Evaluation of Biological Control of Siphoninus phillyreae (Haliday) by the Parasitoid Encarsia partenopea (Walker), Using Life-table Analysis, UC Riverside, Biological Control
- Universal Chalcidoidea Database, Natural History Museum of London
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Aphelinidae
