Aphid killing parasitic wasp, Aphelinus abdominalis are tiny wasps that have been used as an excellent biological control agent in controlling various species of aphids that cause a serious damage to many economically important crops grown in the greenhouses, fields, organic vegetable gardens and orchards. These small parasitic wasps are naturally found in North America and also commercially available.
1. Aphid parasitic wasps, Aphelinus abdominalis is effective against following aphid species [Figs. 1 & 2].
- Alfalfa aphid, Acyrthosiphon pisum
- Bird cherry-oat aphid, Rhopalosiphum padi
- California Laurel aphid, Euthoracaphis umbellulariae
- Cereal aphid, Sitobion avenae
- Cotton aphid, Aphis gossypii
- Green peach aphid, Myzus persicae
- Melon aphid, Aphis gossypii
- Potato aphid, Macrosiphum euphorbiae
2. Key factors influences the effectiveness of aphid parasitic wasp, Aphelinus abdominalis
- Aphelinus abdominalis wasps are small natural parasites of aphids.
- Adults of Aphelinus abdominalis are attracted to the colonies of aphids by responding to alarm signals produced by aphid infested plants and smell of honeydews secreted by aphids on the infested plants.
- Aphelinus abdominalis larvae are parasitic in nature feeding on the body content of aphids whereas their adults feed on honeydews secreted by aphids and directly aphids.
- As a preventive measure Aphelinus abdominalis wasps perform better against aphids when aphid population is at very low level in the garden.
- The preventive applications of Aphelinus abdominalis will prevent out-break of certain species of aphids.
- Remove all the yellow sticky traps used for whitefly control before releasing wasps in your gardens, greenhouse, fields and orchards, as the adult Aphelinus abdominalis wasps are generally attracted to yellow sticky traps and get killed before they can parasitize aphids by laying eggs in aphid body.
- If ants are present on aphid infested plants in your garden or greenhouse, control them first before releasing Aphelinus abdominalis wasps because ants will defend aphids from predators and parasites to protect their honeydew food. If ants are not controlled, effectiveness of wasps as a parasite will be reduced.
- Aphelinus abdominalis wasps perform better against aphids when temperatures in the greenhouses are between 21°C [70°F] and 25°C [77°F] and relative humidity between 60 and 80%.
3. How Aphelinus abdominalis are applied in the greenhouses or fields?
- Aphelinus abdominalis are generally shipped as ready-to-emerge mummies [Fig.3] containing wasp pupae in small vials.
- When package is arrived and if you are not ready to release wasps in your garden, store packages in a cool place [10°C (50°F)] and avoid direct exposure to sunlight.
- It is always better to release these wasps in the field within 15-20 hours of their arrival or storage.
- As a preventive measure, try to release adult wasps that are already emerged from mummies by opening vials and walking slowly in the garden. Adult wasps should escape themselves from the vials. Then randomly place the un-hatched mammies [Fig.3] in shaded areas in the garden.
- As a curative measure, aphid mummies or hatched adults should be released directly in the colonies of aphids or in the heavily infested areas with aphids in the vegetable gardens, greenhouses or fields.
4. How many parasitic Aphelinus abdominalis wasps are required for effective control of aphids?
- As both preventive and curative measures, release 1-2 Aphelinus abdominalis per square meter area for effective control of aphids.
5. How Aphelinus abdominalis wasps work in the greenhouses or fields?
- Aphelinus abdominalis are generally shipped as ready-to-emerge mummies (see below).
- When aphid mummies containing wasp pupae [Fig.3] are applied in the vegetable gardens, greenhouses or fields, adult wasps immediately start emerging from aphid mummies (sometime in the package you may see some already emerged wasp adults).
- Emerged adults of Aphelinus abdominalis will be attracted to colonies of aphids by responding to alarm signals produced by aphid infested plants and smell of honeydews secreted by aphids on the infested plants.
- When adult wasps come across to colonies of aphids, they will select a suitable size aphid using their antennae to lays in the aphid body.
- Once an appropriate size aphid is found, adult wasp turn around and extend and insert its ovipositor tip into the abdomen (ventral side) of aphid and then lay eggs.
- Wasp eggs hatch within the aphid body and hatched young larvae start feeding on the body content of aphid and complete its development within the aphid body.
- The parasitized aphids will survive, reproduce and feed on plant tissue for a while but eventually they will die when the larvae of Aphelinus abdominalis wasp mature and pupate.
- The dead aphids then turn into “mummies” which are commercially sold to use as biological control of aphids [Fig.3].
- After 14- 15 days, adult wasps will start emerging from mummies and life cycle continues.
- Aphelinus abdominalis wasps perform better against aphids when temperatures in the greenhouses or in vegetable gardens are between 21°C (70°F) and 25°C (77°F) and relative humidity between 60 and 80%.
6. Why you need Aphelinus abdominalis wasps?
- they can reduce the crop damage by parasitizing and killing various species of aphids, which are responsible for the damage
- they can parasitize all the different stages of their aphid host species
- they are able to actively search for their aphid hosts and parasitize and kill them
- they can reproduce and continue their life cycle on aphids in your garden after first application
- they are commercially available and easy to apply in the greenhouses or fields
7. Why parasitic Aphelinus abdominalis wasps are safer than traditional pesticides?
- they do not cause damage to plants
- they can be used and applied around children and pets
- they do not cause any harm to the personnel involved in their production and application
- food products are safe to handle and eat when they are treated with wasps
- they do not harm humans, animals and pollute the environment
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