Description

Appearance

---Egg, larva and pupa

Aphelinus abdominalis develop inside aphid (host), which turns into a black mummy (husk of a parasitized aphid) as the parasite (aphelinus abdominalis) develops

Adult

Tiny (≈1/8 inch or 3 mm) winged, non-stinging wasp. It is dark colored, with a pale abdomen and a yellow band across the front, and yellow antennae and legs.

Behavior

A female stings an aphid and then either sucks its juices out through the hole (host feeding) or lays one egg inside it. It can parasitize any aphid life stage, but prefers to parasitize second and third aphid instars. First and second instars are usually used for host feeding. Male eggs are more likely to be laid in smaller instars, while the mother wasp chooses larger instars for its female eggs.

When the egg hatches, the larva feeds on the aphid from the inside and "mummifies" the aphid when it is ready to pupate, turning the aphid into a black husk. The wasp cuts a neat, round escape hole in the rear of the aphid and escapes when mature. Egg laying is low the first few days after emergence, but after the first three days, adult females lay up to 15 eggs a day to a grand total of over 200 eggs in their lifetime. They kill two aphids a day by host feeding.

Adults generally walk or hop, rather than fly. Adults can survive temperatures close to freezing for at least two weeks, and pupa are tolerant of longer periods and may be able to overwinter.

Environment

Activity reduced above 86 °F

Lifecycle

Egg to adult

21 days at 20 °C

Egg and larva

7 days

Pupa

14 days

Adult

15-27 days

Care/Handling

Receive

Packaged in vials of 250 wasp pupae within parasitized aphid [def:mummies:blackened parasitized aphid husks]. Healthy emerged adults may be visible crawling, hopping, or flying around the vial.

Hold

Store at 43-46 °F (6-8 °C). Use within 18 hours of receipt. Keep vial out of direct sunlight or hot vehicles.

Release

Open the vial inside the greenhouse. Hold open vial at a 45 degree angle and walk around area to be treated, tapping the vial gently and letting adults fly out where you see aphids. Be sure to distribute evenly. Recap tube and incubate at greenhouse temperature until more adults have emerged. A shaded place under the plants is a good spot for this. Repeat daily for 2-4 days, until most of the mummies left in the vial should be empty and have emergence holes on one end. After the final release, leave the open vial under a plant horizontally to allow any remaining adults to emerge.

For curative use, release wasps in hot spots, directly under aphid colonies. Open vial and rest it against the base of the infested plant.

Do not remove mummies from vial, as this will reduce their emergence.

Release Rates

General

Release weekly.

Preventive:

2-5 per 100 sq ft (10 sq m)

800-2,000 per acre (2,000-5,000 per hectare)

1 vial per 5,000-13,000 sq ft (500-1,250 sq m)

Curative:

10-25 per 100 sq ft (10 sq m)

4000-10,000 per acre (10,000-25,000 per hectare)

1 vial per 1,000-2,600 sq ft (100-250 sq m)

Other Considerations

Aphelinus abdominalis is most effective as a preventive. Release proactively before aphids become established and as incoming migrating winged aphids appear in the crop.

Not very effective against high numbers of aphids. Use with predators such as Aphidoletes aphidimyza or Green Lacewing  for heavy infestations.

Pests/Crops

Pests Controlled

Greenhouse aphids, potato Macrosiphum euphorbiae and foxglove Aulacorthum solani aphids.

Does not provide good control for cotton/melon Aphis gossypii, green peach Myzus persicae or tobacco aphid Myzus nicotianae.

Additional Benefits

Has been recorded parasitizing a wide range of aphid species, including rose-grain Metopolophium dirhodum, bird cherry-oat Rhopalosiphum padi and grain aphids Sitobion avenae. Also parasitizes green peach aphid Myzus persicae, but Aphidius colemani is a more effective control.

Used In

Greenhouse crops

Success with Aphelinus abdominalis

Best used as a preventive, will not control heavy aphid infestations alone. For heavy outbreaks, reduce aphid numbers before release and use with an aphid predator such as Aphidoletes aphidimyza or a general predator such as Green Lacewing

Avoid water stress. Plant stress, and especially water stress, may lead to a higher male:female parasite population, which can decrease effectiveness of control.

More cost effective for greenhouse use, not very effective outdoors.

 Monitoring

Monitor for adult aphids through plant inspections, sticky cards and trap plants.

 Sticky cards only trap winged aphids, physical inspection of plants is the best way to spot early infestations.

- In greenhouses, place traps near possible entry points, such as vents and doorways.

- Trails of ants can also indicate aphid populations.

Monitor Aphelinus success by looking for black aphid mummies. Aphelinus leaves smooth, circular escape holes when mature.

Cultural Practices

Control ants. Ants protect and care for aphids, and will fight off or eat many beneficials. For more effective ant control, treat for ants in late winter or early spring, when the populations are lowest. Use liquid borate bait in bait dispensers to kill ants. Exclude ants from plants and beneficial release sites with sticky, slippery, or water barriers. See our [link:Ant Control page:rv/ant_management] for more tips.

Spray plants with water to wash off [def:apterous:wingless] aphids and reduce their growth rate.  This also cleans off aphid honeydew.

In greenhouses, aphids can hang around for over a week without having plants to feed on. Clean entire greenhouse thoroughly with an aphid-killing cleaning product, such as soap or orange oil, between crop cycles. Avoid letting aphids get into the greenhouse – screen vents and check clothes, tools and incoming plants for hitchhiking aphids.

Pesticide Compatibility and Toxicity

After release, do not spray pesticides (even soft ones) for at least one week, or until after mummified aphids begin to appear.

For high aphid populations, use soft pesticides such as soap or oil a day or two before releasing parasitoids. When using soap, be sure to rinse soap off plants within 24 hours to prevent it from weakening plants or encouraging pathogenic fungal growth. Selective aphicides (ex. pymetrozine, pirimicarb) may also be used before release.

Treat hot spots with soft pesticides or selective aphicides.