Biological Aphid Control with Aphid Parasites

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About Aphid Parasites
The Aphid Parasites or Aphidius colemani is a small parasitic wasp, native to North America. It is a slender, black insect with brown legs and long antennae. Its size depends on the size of the parasitized aphid, but is usually about 2 mm. About 100 eggs are laid in aphids in which the larvae subsequently develop. At 77°F, 10 days are required from egg to adult for Aphidius. At 70o F, two weeks are required for development of the parasite. Up to 200-300 aphids are attacked be each female. Fertilized eggs develop into females and non-fertilized eggs develop into males. The female has a pointed abdomen, while the male's abdomen is round-shaped.

The parasitic wasp finds aphid colonies from a long distance by "alarm signals" produced by an infected plant. At shorter distance it smells the honeydew. The adult Aphidius feeds on honeydew. Upon detection of an Aphidius in an aphid colony, aphids often secrete "alarm pheromones". Other aphids start to panic, and drop to the ground and die.

Parasite Life Cycle
The female Aphidius deposits an egg in each aphid. She bends her abdomen under her legs and injects an egg in to the aphid with her ovipositor. This takes only a fraction of a second. The wasp parasitizes adults and nymphs. During the egg stage of the wasp (the first 3 days after parasitism), the aphid will eat more than normal and secrete more honeydew.

Thereafter, the Aphidius larva starts eating the aphid from inside, starting with the non-vital parts. Seven days after parasitism (at 70°F) the Aphidius fixes the aphid onto the leaf, and forms a silken cocoon that makes the aphid swell. The outside of the aphid becomes brown and leather-like, and is then called a mummy. Four days after the beginning of the mummification (at 70°F) an adult Aphidius leaves the mummy through a round hole they create and seek out another host.

The total development of Aphidius colemani takes 14 days at 70°F, which is longer than aphid development in optimal circumstances (9 days). However, this is largely compensated by the hundreds of eggs Aphidius lays. The main part of these eggs is laid during the first 4 days. An adult Aphidius lives for 2-3 weeks. Male Aphidius are born out of unfertilized eggs that are deposited soon after mating or at the end of the female's life. The ratio of females to males is usually about 2:1.

Preferred Food
Aphidius can parasitize about 40 aphid species, primarily the green peach aphid and closely related species. This species occurs naturally outdoors and frequently parasitizes aphids in green houses. Aphidius is a good searcher, and can locate new aphid colonies when aphid populations are low.

Shipment And Release Rates
Aphidius is shipped as parasitized aphid mummies from which adults will emerge. Apply 500 to 3,000 Aphidius per acre, 2 to 3 times at one-week intervals, depending upon the extent of infestation.

Warranty
ARBICO makes no guarantee of effectiveness due to subjectivity of application. ARBICO does guarantee live Aphidius colemani - Aphid Parasites upon arrival of product and provides telephone backup for customer questions or problems.