Hosts or Prey
Bluegum psyllid and rosegum psyllid
Identification
Parasitoid presence is most easily recognized by the occurrence of crusty, puffy (mummified) hosts. Several days after feeding inside as a larva the parasitoid causes psyllid nymphs to become mummified. After pupating and emerging as an adult the wasp leaves a circular hole in the psyllid it mummified and killed.
Adult P. pilosus are about 1/25 inch (1 mm) long with a dark blue-green head and blackish abdomen and thorax. Eggs, larvae, and pupae occur hidden inside host psyllids. Eggs and pupae are oblong and larvae are maggotlike. Eggs and larvae are whitish as are young pupae. As they age pupae blacken and develop distinct appendages folded against the body.
Life Cycle
Psyllaephagus pilosus develops through 4 life stages: egg, larva, pupa, and adult. Adult females lay a single egg into a psyllid nymph. The adult female wasp can live for several months and during her lifetime lay an average of about 126 eggs.
The hatching wasp larva feeds inside the psyllid consuming its body contents and mummifying and killing the psyllid. Pupation occurs within the mummified covering of the psyllid. The adult wasp emerges from mummified psyllids after chewing a jagged-edged, rounded hole in the mummy.
In addition to the psyllids killed by parasitization, female P. pilosus also host feed. The female wasp punctures psyllid bodies with her ovipositor and consumes the exuding body contents. Host feeding increases the wasp's longevity and the number of eggs she can lay. Host feeding kills additional psyllids without laying an egg in them.
Egg to adult development time is about 2 to 3 weeks when temperatures are warm. Psyllaephagus pilosus has several generations per year.
Habitat
Bluegum psyllid was inadvertently introduced into California in 1991. It infests several species of eucalyptus, primarily blue gum and baby blue gum. For example it was causing severe defoliation and honeydew fouling of baby blue gum, which is commercially grown for use as cut foliage in flower arrangements. Psyllid infestations made the plants unmarketable.
The psyllid's introduction prompted the University of California to initiate a search for natural enemies in Australia and New Zealand where the psyllid is native. There P. pilosus was collected. After study in quarantine demonstrated this wasp preys on only two species of exotic (introduced, invasive) psyllids the wasp was mass reared and released in California in 1993.
The parasitoid spread throughout the state wherever its hosts occur. Within 6 months of the parasitoid's introduction, baby bluegum growers who had been making frequent insecticide applications to control the psyllid were no longer spraying for this pest. Bluegum psyllid is now difficult to find and no longer a pest because of its successful classical biological control.
Species
At least six species of Psyllaephagus occur in California. Psyllaephagus bliteus, P. brachiatus, P. pachypsyllae, P. parvus, P. perplexus, and P. pilosus. In California bluegum psyllid and rosegum psyllid are the only reported hosts of P. pilosus.
More Information
- Biocontrol of Eucalyptus Psyllid Ctenarytaina eucalypti by the Australian Parasitoid Psyllaephagus pilosus: A Review of Current Programmes and Their Success, Biocontrol News and Information
- Biological Control of the Blue Gum Psyllid Proves Economically Beneficial, California Agriculture
- Parasitoid Wasp Controls Blue Gum Psyllid, California Agriculture
- Universal Chalcidoidea Database, Natural History Museum of London
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Encyrtidae
