Hosts or Prey
California red scale and various other armored scales
Identification
An irregularly shaped hole in the cover of armored scales indicates the activity of C. bifasciata or related parasitoids. Removing scale covers with holes can expose a mummified scale body also containing a hole. Removing the cover of nearby scales without holes may reveal a parasitoid larva or pupa visible through the covering of the host's body.
Adults of C. bifasciata are about 1/16 inch (1.5 mm) long and mostly black with 2 white stripes on top of the head. Females have especially prominent white, head stripes and additionally have contrasting black and whitish areas on the wings. Males have a black body and clear wings without whitish coloration. Males' antennae have numerous fine hairs.
The parasitoid's oval eggs, elongate larvae, and oblong pupae occur hidden within the body of parasitized scales. Eggs, larvae, and initially the pupae are pale to translucent. As they age pupae darken and develop distinct appendages folded against the body. The last instar and pupa are about 1/16 inch (1.5 mm) long.
Lookalikes
Encarsia pernisiosi is another common, internal parasitoid of California red scale. Like C. bifasciata it leaves a puffy, mummified scale body with a hole after feeding inside its host. These parasitoids are readily discriminated from Aphytis species, such as Aphytis melinus, which is an external parasitoid that leaves a shriveled scale body after feeding attached to the outside of the host.
Each of these parasitoids prefers to attack certain life stages of the scale. In comparison with A. melinus and C. bifasciata, E. pernisiosi tends to oviposit in and emerge from smaller, earlier-instar hosts. In comparison with the small, round, emergence hole that adult A. melinus and E. pernisiosi leave in the scale cover, C. bifasciata leaves a larger, more irregularly shaped exit hole in the cover when it emerges.
Life Cycle
Comperiella bifasciata develops through 4 life stages: egg, larva, pupa, and adult. The mated adult female lays about 50 eggs during her lifetime, generally 1 egg per scale. She prefers to oviposit in third-instar and mated female scales, but will oviposit in almost any scale stage except for females that have begun producing crawlers. Comperiella eggs cannot be observed without dissecting the host.
Larvae develop through several increasingly larger instars as they feed inside the scale body. When the larva molts into a prepupa (inactive last instar), it excretes fecal pellets (meconium) that remain inside the scale body, pushed to the sides. When viewed through the dead scale's cover the feces appear as dark crescents.
The pale prepupa develops into a black pupa and then into an adult that chews an exit hole in the scale body and cover. The emerging adult wasp leaves behind a parchmentlike, bloated scale skin (mummy). These mummies usually stay glued to the plant surface, but they may drop off fruit as the fruit grow.
Egg to reproductive adult development time is about 1 month when temperatures are warm. Comperiella bifasciata has several generations per year.
Habitat
Comperiella bifasciata is common in the Central Valley and southern interior areas of California. It occurs at low densities in coastal growing areas. Although C. bifasciata is a common parasitoid of California red scale, Aphytis is the commercially available species recommended for augmentative releases. Comperiella cannot compete against Aphytis because Aphytis, as the external parasitoid, consumes both the scale any Comperiella larva it may contain. Unlike Aphytis-parasitized scales, which readily drop or wash off of fruit, scales parasitized by Comperiella often remain attached to fruit rinds and this is aesthetically undesirable when marketing the fruit.
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., 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 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
Comperiella bifasciata was introduced in California from Asia. It parasitizes at least 36 species of armored scale. Comperiellaunifasciata is the only other Comperiella species reported in California. It also parasitizes California red scale and at least 7 other scale species.
More Information
- Catalog of Hymenoptera in America North of Mexico. Vol. 1: Symphyta and Apocrita (Parasitica), U.S. Department of Agriculture
- Integrated Pest Management for Citrus, UC Integrated Pest Management Program
- Life Stages of California Red Scale and Its Parasitoids, UC Agriculture and Natural Resources
- Observations on Comperiella bifasciata, an Endoparasitoid of Diaspine Coccids, Annals of the Entomological Society of America
- Universal Chalcidoidea Database, Natural History Museum of London
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Encyrtidae
