Aphid Aphidius Parasitoids / Home and Landscape / UC Statewide IPM Program (UC IPM)

Hosts or Prey

Aphids, including the common green peach aphid, melon aphid, and pea aphid

Identification

The most obvious evidence these tiny parasitoids are present is that several days after being parasitized by an Aphidius or another Aphidiidae the aphid becomes a crusty, puffy, smooth mummy that is brown, gold, or tan colored. When parasitized by a family Aphelinidae wasp the mummified aphids turn black.

At least some of the mummified aphids may have a rounded hole left by an emerging adult wasp. The bodies of unparasitized aphids are soft, have no holes visible to the naked eye, and are the color(s) characteristic of the species. However, because the immature parasitoid does not change an aphid's appearance until about a week after the parasitoid egg is laid, the percentage of parasitized aphids can be greater than the percentage of mummified aphids.

Adult Aphidius are slender, black and yellowish wasps 1/8 inch (3 mm) or less in length. They have long, thin, beadlike antenna. The abdomen is elongate and tapers at the rear end.

Aphidius eggs, larvae, and pupae occur hidden within parasitized aphids. The elliptical, white eggs and first instars are about 1/250 inch (0.06 mm) long. Larvae are pale colored or white, legless, and have distinct segments. The maggotlike larvae have a tail-like rear in the first 2 instars but not in the more plump last instar. Last instars are about 1/12 inch (2 mm) long. Curved or hooked mouthparts may be apparent on the head end.

Pupae are oblong with distinct segments. As they age they develop appendages folded against the body.

Life Cycle

Aphidius species develop through 4 life stages: egg, larva, pupa, and adult. Each adult female lays 1 egg in about 100 aphid nymphs of any size. After hatching the larva develops through 3 increasingly larger instars as it feeds on the aphid's insides. About 7 to 10 days after the egg was laid the mature wasp larva (prepupa) kills the aphid and causes its skin to become crusty and puffy (mummified). The wasp then pupates into an adult that chews a rounded hole and emerges from the mummy.

Egg to reproductive adult development time is about 2 weeks at summer temperatures. Aphidius species have several generations of per year.

Habitat

The genus Aphidius contains many species that provide biological control of aphids in agricultural crops, gardens, greenhouses, and landscapes.

Commercial Availability

Some species of Aphidius are mass produced and sold for release to improve biological control of aphids. To conserve resident natural enemies and any that may be released

Control ants because they attack natural enemies.
Grow flowering insectary plants to provide nectar for adult parasitoids.
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 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

More than 1 dozen Aphidius species occur in California. Each Aphidius species parasitizes numerous species of aphids. For example A. colemani and A. matricariae each parasitize at least 40 species of aphids.