Aphid Parasites

Parasites feed on other organisms. Aphid parasites feed on aphids. Let’s see what we can find out about these tiny garden helpers.

Aphid parasites (Aphidius colemani) and greenhouse aphid parasites (A. ervi) are parasitic wasps, but you don’t have to worry about getting stung. These native North American braconid wasps are more interested in aphids, honeydew, and nectar.


Aphid parasite description

Aphid parasite adults are black or brown with a narrow waist. They have yellow legs and long antennae. These tiny predators are only 1/10” long, which means you could put 7 or 8 of them in a line across the top of an American dime. You’ll probably never see aphid parasite larvae. They are very tiny and white, grub-like creatures.

Aphid parasite with Russian wheat aphids (Frank Peairs, Colorado State University, Bugwood.org) CC BY 3.0 US

Greenhouse aphid parasite (Matt Bowser, U.S. Fish and Wildlife Service) Public Domain

Aphid parasite lifecycle

Females only mate once. After mating, they fly in search of aphid hosts for their young. Aphid parasites insert single eggs inside 100 aphids, and their greenhouse cousins lay up to 300 eggs. When those eggs hatch, the larvae eat their host aphids from the inside out. Ouch!

Aphid parasites often cut holes in the underside of their hosts to attach anchoring threads to a leaf. After about a week, these parasitized aphids swell up like balloons and turn beige to brown. These puffed-up aphids are called mummies. The larvae pupate inside the aphid and emerge as adults, ready to continue the cycle.

Parasitized aphid (Katja Schulz) CC BY 2.0

Surviving aphids frequently emit “alarm” pheromones that cause neighboring aphids to jump ship, abandoning the host plant and falling to the ground where they often die of starvation. Just as well.

Adult aphid parasites only live for 2 or 3 weeks, feeding on aphid honeydew and nectar from small flowers, such as anise, dill, mustard, and parsley. Their offspring can parasitize a large number of aphids. Aphid parasites are most active when temperatures are between 64°F and 77°F. They prefer green peach aphids and melon aphids for their supper but eat other aphid species, too.

Aphids and parasitized "mummies" hosting aphid parasites (Whitney Cranshaw, CSU, Bugwood.org) CC BY 3.0 US

Aphid parasites are available commercially and are frequently used to control aphids in greenhouse environments. You can attract and maintain habitat for aphid parasites by planting clumps of rye or barley. These plants attract aphids, providing a long-term food source for your aphid parasites. You can also add the flowers mentioned earlier. Because aphid parasites can fly, they will regularly scan your garden for all sorts of aphids. You should start seeing aphid mummies 10 to 14 days after releasing these hunters into your garden.