Hosts or Prey
Asian citrus psyllid (ACP)
Identification
Parasitism by T. radiata can be observed in the field because the emerging adult wasp leaves a circular exit hole in the crusty, puffy (mummified) Asian citrus psyllid (ACP) it killed. The wasp does not mummify its host until a week or more after the parasitoid egg is laid, but if the sides and underside of ACP nymphs near mummies are examined with a hand lens some of those are likely to have an egg or larva of T. radiata attached to their body.
The adult T. radiata is a wasp about 1/25 inch (1 mm) long. The head and thorax are black. The bulging eyes are dark red. The abdomen and appendages are mostly whitish or yellowish. In comparison with females the males have a darker abdomen and longer antenna with numerous, long, slightly curved hairs.
Parasitoid eggs, larvae, and pupae occur hidden inside or underneath parasitized psyllids. The egg is translucent to white and kidney shaped (circular with a notch). Larvae are legless and orangish with distinct segments. They are globular and tapered on one end. The pupa is oblong and initially pale. As it ages the body blackens, red eyes develop, and distinct appendages develop folded against the body.
Life Cycle
Tamarixia radiata develops through four life stages: egg, larva, pupa, and adult. The adult female wasp injects venom that paralyzes psyllid nymphs but does not kill them. She then deposits one egg beneath a psyllid nymph attached to an appendage or its body. If more than one egg is laid on a nymph generally only one wasp will survive to maturity.
A female T. radiata deposits on average 200 eggs during her lifespan of about 3 weeks. Fertilized eggs produce female wasps and unfertilized eggs produce males. Any instar (nymphal stage) of ACP is a suitable host, but the wasp prefers to oviposit beneath fourth and fifth instars. Larger host stages produce greater survival of the wasp and increase the egg laying ability and longevity of female wasps that emerge from them.
In addition to killing hosts by parasitism, adult female wasps kill first through third instars by feeding on them. The female wasp punctures the nymph with her ovipositor and consumes the exuding body contents. A female wasp may host feed on and kill dozens of psyllid nymphs during her lifetime. Host feeding increases the wasp's longevity and egg laying. Both genders feed on honeydew and this also increases their longevity.
After hatching from an egg the first instar feeds beneath the nymph attached to its outside where it sucks the body contents. Late instar larvae commonly move to the side of the nymph to feed. Tamarixia radiata develops through 4 increasingly larger instars as it feeds. All contents of the nymph are consumed by the time the parasitoid molts to the fourth instar and the nymph becomes brown, crusty, and somewhat swollen (mummified). After pupating the adult wasp chews a round hole about 1/50 inch (0.5 mm) in diameter on top of the mummy and emerges.
Egg to reproductive adult development time is about 2 weeks when temperatures are warm. Tamarixia radiata has multiple generations per year.
Habitat
In 2008 the exotic Asian citrus psyllid was found in Southern California. In addition to weakening citrus trees by feeding on them the psyllid vectors the bacterium that causes huanglongbing disease that has also become introduced in Southern California. The bacterium causes citrus fruit to become unpalatable and gradually kills infected citrus trees and certain other plants in the Rutaceae family.
As part of a classical biological program entomologists from UC Riverside collected T. radiata in Pakistan, which is believed to be the native range of the psyllid. After studies under quarantine in California indicated that T. radiata is not harmful to beneficial species, the parasitoid was released in Southern California beginning in 2011. The wasp now occurs throughout much of Southern California where Asian citrus psyllid occurs.
Tamarixia radiata significantly reduces psyllid abundance if ants are controlled to prevent them from attacking the adult parasitoids. Predators that feed on Asian citrus psyllid include larvae of syrphid flies and various lady beetles (ladybugs or ladybird beetles). To improve biological control
- Control ants because they attack natural enemies of psyllids and other pests.
- Grow flowering insectary plants to provide nectar for adult natural enemies.
- Reduce dustiness that disrupts the activities of natural enemies (e.g., periodically hose off small plants).
- Avoid the application of broad-spectrum, persistent insecticides for all pests because they are toxic to natural enemies.
See Selectivity of Insecticides and Miticides used in citrus and Protecting Natural Enemies and Pollinators for more information.
Species
At least four species of Tamarixia occur in California. Tamarixia dahlsteni, T. radiata, T. schina, and T. triozae. All were deliberately introduced to control exotic, invasive psyllids. Asian citrus psyllid is the only known host of T. radiata in California.
More Information
- Biocontrol Program Targets Asian Citrus Psyllid in California's Urban Areas, UC Riverside, California Agriculture
- Biological Control of Asian Citrus Psyllid in California, UC Riverside
- Biology of Tamarixia radiata (Hymenoptera: Eulophidae), Parasitoid of the Citrus Greening Disease Vector Diaphorina citri (Hemiptera: Psylloidea): A Mini Review (PDF), Florida Entomologist
- Common Name: An Asian Citrus Psyllid Parasitoid Scientific Name: Tamarixia radiata (Waterston) (Insecta: Hymenoptera: Eulophidae), University of Florida
- Pest Management Guidelines: Citrus, UC Integrated Pest Management Program
- Pest Notes: Asian Citrus Psyllid and Huanglongbing Disease, UC Integrated Pest Management Program
- Tamarixia radiata Waterston [Hymenoptera: Eulophidae], an Ectoparasitoid of Diaphorina citri Kuwayama [Hemiptera: Psyllidae], Cornell University
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Eulophidae
