Hosts or Prey
Mealybugs
Identification
Acerophagus notativentris apparently is the most common and important of the Acerophagus species in California so discussion below focuses on it. The most obvious evidence of an Acerophagus species or similar parasitoid is the presence of crusty, orangish, swollen mealybugs that have been mummified by the immature wasps. After killing the mealybug and pupating inside its host the adult wasps leave one to several roundish emergence holes in the mealybug's mummified covering.
The adult A. notativentris is 1/50 to 1/32 inch (0.5–0.8 mm) long, varying by gender, host size, and the number of parasitoids the host contained. Adults are bright yellow or orangish wasps with brown markings on top of the abdomen. They have green eyes and clear wings.
The pale eggs, maggotlike larvae, and oblong pupae occur hidden inside of mealybugs. The egg is about 1/300 inch (0.08 mm) long and oval spherical with a slender stalk of about the same length. The legless larva is initially elongate but becomes plump and saclike as it matures. The mature larva and pupa are about 1/40 inch (0.6 mm) long. As the pupa matures distinct appendages develop folded against the body.
Life Cycle
Acerophagus species develop through 4 life stages: egg, larva, pupa, and adult. The adult female wasp oviposits in any instar nymph or adult female of grape mealybug and several other mealybug species. Fertilized eggs produce female wasps and unfertilized eggs produce males. From 1 to about 25 parasitoids can complete development in a single mealybug. Only 1 adult wasp emerges from parasitized first instars (nymphs) but multiple wasps emerge from later, larger instars or adult females.
Acerophagus notativentris and Pseudaphycus angelicus are the dominant parasitoids of grape mealybug in California vineyards. Adult A. notativentris are active from spring through fall, especially during spring and summer. Overwintering is as eggs or larvae in nymphs of host mealybugs.
Egg to reproductive adult development time is about 3 weeks during the summer. Acerophagus notativentris has several generations per year.
Habitat
Acerophagus notativentris apparently is native to California. It can occur wherever grape mealybug or its other hosts occur, which includes grapes and pears. Where the use of broad-spectrum, persistent insecticides is avoided and ants are controlled A. notativentris can be the most common of several natural enemies that can keep grape mealybug abundance at nondamaging levels.
To improve biological control
- Control ants because they attack natural enemies of mealybugs 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., 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.
To learn what pesticides are compatible with biological control of mealybugs see Relative Toxicities of Insecticides and Miticides Used in Grapes to Natural Enemies and Honey Bees and Relative Toxicities of Insecticides and Miticides Used in Pears to Natural Enemies and Honey Bees. To learn of other practices that can increase biological pest control see Protecting Natural Enemies and Pollinators.
Species
At least 13 species of Acerophagus occur in California. All are parasitoids of various species of mealybugs or scale insects. Acerophagus notativentris parasitizes at least 8 species of mealybugs. Its economically important hosts include Comstock mealybug, grape mealybug, and obscure mealybug. Acerophagus maculipennis also parasitizes these 3 mealybugs.
More Information
- Annotated Checklist of California Encyrtidae (Hymenoptera) (PDF), UC Berkeley, Zootaxa
- The Parasitoids of Pseudococcus maritimus (Ehrhorn's) in California (Hymenoptera, Chalcidoidea) Part II. Biological Studies and Life Histories, University of California Publications in Entomology
- A Systematic Study of the Genus Acerophagus E. Smith With Descriptions of New Species (Hymenoptera: Encyrtidae), UC Riverside, Hilgardia
- Universal Chalcidoidea Database, Natural History Museum of London
- Vineyard Managers and Researchers Seek Sustainable Solutions for Mealybugs, a Changing Pest Complex, California Agriculture
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Hymenoptera
- Family: Encyrtidae
