Aphidius Ervi

Aphidius ervi is a species of parasitic wasp of the family Braconidae that lay their eggs in aphids. They are used in the biological method of pest control of greenhouse farms.

Aphidius ervi parasitizes a number of aphid species, but is most often used to control large aphid species such as Aulacorthum solani (glasshouse-potato aphid), Macrosiphum euphorbiae (potato aphid) and Acrythosiphum pisum (pea aphid), on which Aphidius colemani does not parasitize.

Description and life cycle

Aphidius ervi have a black body, about 4-5 mm long. They are very similar to Aphidius colemani, but darker and slightly larger. Adult wasps resemble small winged ants with long and thin antennae.

As soon as the female finds a single individual or an entire colony of aphids, she probes the victim with her antennae. If the aphid she is examining has the right size and is not yet infected with parasites, she quickly bends her stomach under her body and strikes the aphid with her ovipositor. The whole process lasts less than one second, but during this time the female manages to check the compliance of the victim, make a puncture and lay an egg.

Soon, a larva emerges from the egg, which begins to feed on the victim. Initially, it does not kill the host, but as it grows, it begins to feed on vital organs, so that in the end the carrier dies. When the Aphidius ervi larva is fully grown, it cuts a gap in the body of its host and attaches itself to it with silk. As more silk is spun in the host’s skin, it gradually acquires a pale gray colour and forms a characteristic “aphid mummy”.

Inside the mummy, the larva pupates, and after 5-10 days passes into the imago stage. The adult cuts a round hole in the mummy, always on the back upper surface, and comes out of it in search of new hosts.

The life cycle of Aphidius ervi takes about 19 days at 22 °C and about 12 days at 25 °C. This is more than the time of aphid development, but each Aphidius ervi female is able to parasitize more than 300 aphids during a lifetime of 2-3 weeks, under favourable conditions.

Prolonged temperatures above 30 °C or below 8 °C negatively affect the parasitoid wasp’s performance.

Suitable crops

Aphidius ervi can be used on all crops impacted by aphids. It is mainly used in greenhouse production, but it can also be used outdoors so that parasitoids appear earlier than they do in nature. Aphidius ervi will be useful for crops such as peppers, aubergines, roses and other flower crops, a number of ornamental plants and some field crops such as alfalfa, legumes, and potatoes.

When to release?

Aphidius ervi works best when used prophylactically or when aphids are first detected on a crop. This parasitoid disperses very well and finds aphid populations. If the aphid population is already high, it is recommended to use a non-destructive insecticide to reduce the aphid population before releasing the entomophage. Broad-spectrum insecticides with high residual properties should be discontinued at least 4 weeks before the release of the parasitoid wasp. If several aphid species are present, it is recommended to release Aphidius ervi together with Aphidius colemani to cover a wider range of pest species.

How to release?

Aphidius ervi are supplied in the form of aphid mummies. Given the life cycle, during the delivery time, usually some of them become adults. The release of the entomophage should be carried out as soon as possible. If there is no such possibility, then they can be stored at 8-12 °C for no more than one day.

The release of the entomophage is carried out quite simply, taking into account the independent ability to disperse. It is necessary to open the container with the parasitoid next to the culture that needs to be protected. After that, some of the individuals who have become adults will leave it on their own and disperse around the site. The remainder of the mummies in the vial should be distributed over the treated area, sprinkling them on the foliage or leaving an open vial under the foliage at the base of the plants.

Release standards

The norms will vary depending on the type of target aphid and the level of infection at the time of release. The following standards have been identified to control Aulacorthum solani and Macrosiphum euphorbiae in greenhouse vegetables and can be used as a guideline.

Prevention: 0.1 / m2 per week.

After aphid detection: 0.5/m2/week and up to 10/m2 for hot spots, for at least 3 weeks.

Compatibility with pesticides

Aphidius ervi are sensitive to many pesticides, especially pyrethroids, organophosphates and neonicotinoids. Residues on foliage and greenhouse structures can remain toxic for many weeks and negatively affect survival, population formation and the ability to control the phytophage. Carefully check the schedules of side effects, and avoid the use of pesticides before and during the use of Aphidius ervi. Contact specialists for advice.