Hosts or Prey
Navel orangeworm and various other caterpillars
Identification
The adult is an elongate, shiny, blackish wasp about 1/6 inch (4 mm) long. It has brown antennae and legs and a bluntly pointed rear end.
The pale orange to whitish eggs and larvae occur attached to the outside of parasitized caterpillars. The oblong eggs are about 1/50 inch (0.5 mm) long. Larvae have distinct segments and at maturity are about 1/5 inch (5 mm) long.
Pupae occur in a silken cocoon attached or near to the dead caterpillar's skin, which becomes shriveled from the wasps' feeding. Inside each cocoon the pupa is initially whitish. It blackens and develops distinct appendages folded against the body as it matures into an adult.
Life Cycle
Goniozus species develop through four life stages: egg, larva, pupa, and adult. Adult females seek medium to large, late-instar caterpillars to parasitize. The adult female G. legneri stings the caterpillar with her ovipositor, usually near the head and injects venom that paralyzes the host. She then walks repeatedly back and forth on top the larva and occasionally bites it, apparently to determine whether it is paralyzed. She sometimes stings the larva repeatedly.
Once the caterpillar no longer moves, usually within about 30 minutes of first being stung, the wasp lays 1 to 20 eggs on the host. The larger the caterpillar the more eggs the wasp deposits on it. An adult female can lay approximately 100 eggs during her lifetime of up to several weeks.
In addition to killing caterpillars by parasitization, female G. legneri host feed, which kills additional caterpillars. The wasp punctures caterpillars with her ovipositor and consumes the exuding body contents. By host feeding the wasp increases its longevity and the number of eggs that she can lay. The female wasp also stings, paralyzes, and causes to die additional caterpillars that she does not feed on or parasitize.
The hatching wasp larvae remain attached to the host as they consume its body contents. The female wasp remains with the parasitized host, apparently guarding her progeny to ward off natural enemies that might attack her young or their host. Females do not leave the host and parasitize another caterpillar until their larvae are nearly mature. When the caterpillar has shrunken down to an empty skin the wasp larvae each spin a silken cocoon and pupate.
Developmental time from an egg to a reproductive adult is about 2 weeks when temperatures are warm. Goniozus species have multiple generations per year.
Habitat
Goniozus legneri was introduced into California from Argentina and Uruguay in 1979 along with a parasitoid from Mexico, Copidosoma plethoricum, to help control navel orangeworm, a primary pest of almonds. Both parasitoids are now established in orchards throughout California.
Goniozus legneri can occur anywhere that any of its numerous caterpillar hosts occur. Its hosts include carob moth, codling moth, navel orangeworm, obliquebanded leafroller, and pink bollworm. Crops where it helps control caterpillars include almond, fig, pistachio, and walnut.
To improve biological control
- Control ants because they attack natural enemies of various pests.
- Grow flowering insectary plants to provide nectar to nourish adult natural enemies.
- 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 table of relative toxicities of insecticides and miticides to natural enemies and honey bees for specific crops.
Commercial Availability
Goniozus legneri is commercially available for purchase and release to help control certain caterpillars. See The Association of Natural Biocontrol Producers, Biological Control Organisms for Insects and Mites (PDF), Natural Enemy Releases for Biological Control of Crop Pests, and Protecting Natural Enemies and Pollinators for more information.
Species
At least 10 species of Goniozus occur in California. These include Goniozus asperulus, G. breviceps, G. emigratus, G. fratellus, G. foveolatus, G. gordhi, G. gracilicornis, G. legneri, G. longinervis, and G. punctaticeps.
More Information
- Establishment of Goniozus emigratus and Goniozus legneri [Hym: Bethylidae] on Navel Orangeworm, Amyelois transitella [Lep: Phycitidae] in California and Biological Control Potential, UC Riverside, Entomophaga
- Goniozus legneri Gordh (Parasitoid of the Navel Orangeworm), photographs by Max E. Badgley, UC Riverside
- Lower Navel Orangeworm (Lepidoptera: Phycitidae) Population Densities Following Establishment of Goniozus legneri (Hymenoptera: Bethylidae) in California, UC Riverside, Journal of Economic Entomology
- Monarch, collections database, California Academy of Sciences
- New Wasp May Help Control Navel Orangeworm, California Agriculture
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Bethylidae
