Hosts or Prey
Glassy-winged sharpshooter and certain other sharpshooters (leafhoppers)
Identification
Sharpshooter eggs that were parasitized by Cosmocomoidea species can be recognized by a tiny, round hole at one end of the egg through which the adult parasitoid emerged. The mass of parasitized leafhopper eggs resembles an elongate, brownish to tan blister in leaf tissue. The parasitoid eggs, larvae, and pupae occur hidden inside sharpshooter eggs that are embedded in foliage. The parasitoids themselves are easily overlooked because they are tiny.
Adult Cosmocomoidea are about 1/50 to 1/16 inch (0.5–1.5 mm) long. They have long antennae and clear wings. The head and thorax are black or orange varying by the species and the abdomen is orange or yellow with black bands or other markings.
The Cosmocomoidea egg is oblong with a stalk, pale, and about 1/160 inch (0.15 mm) long. The head of the first instar is a broad and conical and ends with a sharp hooklike mouthpart. The abdomen and thorax are distinctly segmented and elongate with a pointed rear end. The first instar is approximately 1/160 inch long.
Second and third instars are oval, and shaped like the oblong egg of a glassy-winged sharpshooter. The mature third (last) instar is about 1/70 to 1/16 inch (0.3–1.5 mm) long. As the pupa ages the adult appendages develop folded against the body.
Life Cycle
Adult female Cosmocomoidea lay eggs inside eggs of glassy-winged sharpshooter and certain other sharpshooter species. Most Cosmocomoidea species occur only one per host egg including C. ashmeadi, C. morrilli, C. triguttatus, and C. walkerjonesi. Cosmocomoidea fasciatus develops two or three individuals per host egg and this wasp adult is smaller than those of the other Cosmocomoidea species.
The hatching wasp larvae develop through three increasing larger instars as they feed on the contents of a sharpshooter egg. After pupating inside the adult wasp chews a circular, emergence hole through the egg covering and leaf cuticle.
If honeydew or flower nectar are available, Cosmocomoidea wasps lay more eggs and live about twice as long. If these food resources are available adults of most Cosmocomoidea species live about 2 weeks and C. ashmeadi adults live about 7 weeks. See Insectary Plants for discussion of how to feed and shelter parasitoids to increase the biological control of glassy-winged sharpshooter and various other pests.
During the winter when glassy-winged sharpshooter is not active or laying eggs Cosmocomoidea overwinter as undeveloped larvae in host eggs laid during the fall. Egg to reproductive adult development time is 2 to 3 weeks during the summer and several months during the winter. These parasitoids have several generations per year.
Habitat
Glassy-winged sharpshooter was first found in California in 1990 after it was inadvertently introduced from the Southeastern United States where it is native. It now occurs throughout Southern California and in some Central California locations. It is a major pest because it transmits the bacterium Xylella fastidiosa that causes disease in many crops and ornamentals, such as Pierce's disease lethal to grapes and oleander leaf scorch lethal to oleander and certain other ornamentals.
The presence of glassy-winged sharpshooter prompted entomologists from the California Department of Food and Agriculture and University of California to search for parasitoids of the pest in the Eastern United States, Mexico, and South America. Beginning in 2002 another Mymaridae Anagrus epos and several Cosmocomoidea species (then named Gonatocerus species) were collected. After study under quarantine found the wasps do not attack desirable species the wasps were introduced into California. The introduced species included C. ashmeadi, C. fasciatus, C. morrilli, C. morgani, C. triguttatus, and C. walkerjonesi.
Cosmocomoidea ashmeadi is now commonly found wherever glassy-winged sharpshooter occurs in California, especially later in the growing season. In the southern and coastal areas of California C. walkerjonesi can also be an effective parasitoid in the late summer when the second generation of sharpshooter eggs are deposited. Neither C. ashmeadi nor C. walkerjonesi are normally present at high levels during the first generation of glassy-winged sharpshooter egg laying.
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 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
At least 16 Cosmocomoidea species occur in California. Cosmocomoidea ashmeadi is the parasitoid responsible for most of the parasitism of glassy-winged sharpshooter. It also parasitizes at least 9 other species of sharpshooters.
More Information
- Biology and Morphology of Gonatocerus sp. (Hymenoptera, Mymaridae), an Egg Parasitoid of the Green Rice Leafhopper, Nephotettix cincticeps Uhler (Homoptera, Deltocephalidae), illustrations of immature stages, Kontyû, Tokyo
- A Key to the Mymaridae (Hymenoptera) Egg Parasitoids of Proconiine Sharpshooters (Hemiptera: Cicadellidae) in the Nearctic Region, With Description of Two New Species of Gonatocerus (PDF), Zootaxa
- Illustrated Key to Genera and Catalogue of Mymaridae (Hymenoptera) in America North of Mexico (PDF), Zootaxa
- Introduced Parasitic Wasps Could Control Glassy-winged Sharpshooter, California Agriculture
- Universal Chalcidoidea Database, Natural History Museum of London
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Mymaridae
