Hosts or Prey
Identification
The presence of this parasitoid can often be recognized by a change in the appearance of parasitized hosts. Normally pale greenhouse whiteflies commonly blacken as the E. formosa wasp develops inside of them. When an adult Encarsia emerges from a host it chews a round hole in the covering of the host pupa, which remains darkened. Discolored pellets of Encarsia feces (meconium) can be visible inside the host covering. When a non-parasitized whitefly emerges from its pupal case it leaves a ragged or T-shaped slit in a covering that is transparent to whitish and empty (containing no meconium).
The adult female E. formosa has a black head and thorax, yellow abdomen, and clear wings. The adult's body is about 1/60 inch (0.4 mm) long. The rarely seen male is slightly larger and entirely black except for the clear wings. Eggs, larvae, and pupae occur within host whiteflies.
Lookalikes
When parasitized by Encarsia pergandiella, greenhouse whiteflies turn bright yellow then brown because the brown to yellow E. pergandiella larva or pupa can be observed through the cover of its host. In comparison with parasitization by E. formosa, host covers are pale after E. pergandiella emerges. When Encarsia luteola parasitizes whiteflies they also turn brown to yellow but after the adult wasp emerges the covering of the host pupa remains darkened brown, but not black as with parasitization by E. formosa.
Life Cycle
Encarsia formosa develops through four life stages: egg, larva, pupa, and adult. In addition to the whiteflies killed by parasitization the adult female wasps feed on hemolymph (blood) of whiteflies. The female wasp punctures whitefly nymphs with her ovipositor and consumes the exuding body contents. When whiteflies are host fed upon they die and are not used for parasitoid egg laying. Adults also feed on honeydew and nectar and this increases their longevity.
Adult females lay 1 egg per host in all whitefly life stages except the egg and mobile first instar (crawler). Females prefer to oviposit in whitefly third and fourth instars prior to the pupal stage. An Encarsia female during her approximately 2-week lifespan on average parasitizes about 5 whiteflies per day and host feeds on 3 whiteflies per day.
The hatching Encarsia larva develops through 3 increasingly larger instars as it feeds within its host. The wasp larva feeds inside immature greenhouse whiteflies for about 10 days before turning them black during the host's pupal stage. The last instar wasp pupates inside the whitefly then the adult wasp chews a round hole in the mummified host cover and emerges.
Habitat
Encarsia formosa occurs naturally in the field wherever greenhouse whitefly occurs. It also commonly colonizes greenhouse crops infested with greenhouse whitefly and certain other whiteflies.
Commercial Availability
Encarsia formosa is commercially reared and sold. It has been released for biological control of whiteflies infesting crops, such as floricultural and ornamental nursery plants, tomatoes, and strawberries. Releases of Encarsia are most effective if begun when the numbers of whiteflies are low, only a few whiteflies per plant.
To conserve resident natural enemies and any that are released
- Control ants because they attack natural enemies of whiteflies and other pests.
- Grow flowering insectary plants to provide nectar and pollen to nourish adult parasitoids and predators.
- Reduce dustiness that disrupts the activities of natural enemies (e.g., irrigate overhead or periodically hose off small plants).
- Avoid the application of broad-spectrum, persistent insecticides for all pests because they are toxic to natural enemies.
For more information see The Association of Natural Biocontrol Producers, Biological Control Organisms for Insects and Mites (PDF), Encarsia formosa Hymenoptera Aphelinidae, Natural Enemy Releases for Biological Control of Crop Pests, Protecting Natural Enemies and Pollinators and the table of relative toxicities of insecticides and miticides to natural enemies and honey bees for specific crops.
Species
At least 30 species of Encarsia occur in California. Most parasitize multiple species of scale insects, whiteflies, or other plant-sucking insects formerly called Homoptera. Encarsia formosa parasitizes at least 27 species of whiteflies including the important pests greenhouse whitefly, silverleaf whitefly, and sweetpotato whitefly.
More Information
- Biology and Use of the Whitefly Parasitoid Encarsia formosa, Annual Review of Entomology
- Bionomics of Aphelinidae, Annual Review of Entomology
- Encarsia formosa Hymenoptera Aphelinidae, Cornell University
- A Pictorial Guide to the Species of Encarsia (Hymenoptera: Aphelinidae) Parasitic on Whiteflies (Homoptera: Aleyrodidae) in North America, Proceedings of the Entomological Society of Washington
- Universal Chalcidoidea Database, Natural History Museum of London
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Aphelinidae
