Hosts or Prey
Nymphs of redgum lerp psyllid and several other psyllid species
Identification
The most obvious evidence of activity of this parasitic wasp is a round hole in the waxy coverings (lerps) of its host psyllids. If a lerp with a hole is lifted from the leaf to which it is attached, underneath the cover will be a brown, puffy, mummified psyllid covering that also contains a rounded emergence hole of the adult wasp. If nearby lerps that lack a hole are lifted it is likely that underneath some will be a parasitized or mummified nymph still containing an immature parasitoid. The parasitoid itself may be partly visible through the psyllid's covering.
Adult P. bliteus are wasps about 1/12 inch (2 mm) long. They have clear wings, distinct antennae, metallic green bodies, and yellowish legs. The eggs, nymphs, and pupae are brown, green, or whitish and occur hidden under the lerp and inside the body of the host psyllid, most commonly redgum lerp psyllid, Glycaspis brimblecombei.
The eggs are oblong and about 1/70 inch (0.3 mm) long. Larvae are maggotlike and mature larvae and pupae are about 1/12 inch (2 mm) long. Pupae are oblong and initially whitish. As the pupa ages it darkens and distinct appendages develop folded against the body.
Life Cycle
Psyllaephagus bliteus develops through four life stages: egg, larva, pupa, and adult. A mated adult female can oviposit into psyllid nymphs of any age but she prefers third and fourth instars.
Each female wasp lays approximately 125 eggs during her lifetime. If eggs are laid on psyllid nymphs younger than the late fourth instar the parasitized psyllid continues to feed until it becomes a late fourth or early-fifth instar, at which time the parasitoid larva starts to feed and kills its host.
After killing its host the wasp larva pupates then emerges as an adult, leaving a roundish hole in the psyllid mummy and its lerp cover. Each adult wasp lives for approximately 2 to 6 weeks when temperatures average 80º and 63ºF, respectively.
Egg to adult development time is approximately 2 weeks when temperatures are warm. Psyllaephagus bliteus has multiple generations per year.
Habitat
The eucalyptus redgum lerp psyllid was inadvertently introduced into California in 1998. The psyllid infests over 2 dozen Eucalyptus species planted in California, especially river red gum, flooded gum, and forest red gum. The accumulation of the sticky lerps on leaves and underneath infested trees creates a nuisance and attracts yellow jackets. Abundant psyllids cause premature leaf drop and defoliation, branch dieback, and occasionally tree death.
The pest's introduction prompted the University of California to initiate a search for natural enemies in Australia where the psyllid is native. There P. bliteus was collected. Because this wasp preys on only a few species of exotic (introduced, invasive) psyllids (superfamily Psylloidea) including redgum lerp psyllid, the wasp was mass reared and widely released in California from 2000 through 2002.
Psyllaephagus bliteus now occurs in most California locations where redgum lerp psyllid occurs. The wasp has significantly reduced psyllid populations at coastal locations, especially in southern California. This classical biological control program has been less successful in interior valleys of California apparently because the summer heat reduces the activity, reproduction, and survival of the parasitoid.
To improve biological control
- Control ants because they attack natural enemies of psyllids and other pests.
- Grow flowering insectary plants to provide nectar to nourish 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 Protecting Natural Enemies and Pollinators for more information.
Species
At least six species of Psyllaephagus occur in California. Psyllaephagus bliteus, P. brachiatus, P. pachypsyllae, P. parvus, P. perplexus, and P. pilosus. All are parasitoids of psyllids. Psyllaephagus bliteus parasitizes at least five species of exotic psyllids.
More Information
- The Biology of Psyllaephagus bliteus Riek (Hymenoptera: Encyrtidae), a Parasitoid of the Red Gum Lerp Psyllid (Hemiptera: Psylloidea) , UC Berkeley, Biological Control
- Climate and the Effectiveness of Psyllaephagus bliteus as a Parasitoid of the Red Gum Lerp Psyllid, UC Berkeley, Biocontrol Science and Technology
- Imported Parasitic Wasp Helps Control Red Gum Lerp Psyllid, California Agriculture
- Pest Notes: Eucalyptus Redgum Lerp Psyllid, UC Integrated Pest Management Program
- Red Gum Lerp Psyllid, Center for Invasive Species Research, UC Riverside
- Universal Chalcidoidea Database, Natural History Museum of London
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Encyrtidae
