Aphidius Colemani — Parasitoid Wasp

Aphidius colemani (Hymenoptera: Braconidae) is a single aphid coinobiont endoparasitoid and one of the most successful commercial biological control agents used in greenhouse crops. It is believed that this parasitoid wasp is of Indian or Pakistani origin. For the first time this wasp was used in biological control programs in the early 1970s, and since 1991 it has been massively bred and sold on the market. Aphidius colemani is currently used worldwide and is an economically available entomophage.

Description

Adults are dark with yellow paws, the body is 2-3 mm in length. There are long antennae on the head. These wasps don’t sting. In place of the sting, the females have an ovipositor, with which they pierce the victim, laying offspring.

Life cycle

The larvae fully develop and feed inside the host’s body, which eventually die. When the larva pupates, the body of the aphid becomes a golden-brown mummy. Adults emerge from the mummies by cutting an exit hole in the upper part. The empty mummy remains on the surface of the leaf. The size of the adult parasite and the number of eggs it can lay depends on the size of the aphid in which the development took place.

The full life cycle takes about 10 days at 25 °C and about 2 weeks at 21 °C. The sex ratio in the population is about the same, although there may be slightly more females than males (50-60% of females). Each female lays about 100 eggs during her lifetime, but at the same time can attack 200-300 aphids.

Effectiveness

Aphidius colemani have developed search abilities, and can find new aphid colonies even with a low phytophages population.

Aphidius colemani is mainly used to control economically important aphids Myzus persicae (green peach aphid) and Aphis gossypii (melon or cotton aphid). Peach and cotton aphids are extremely omnivorous and infect a wide range of vegetable and ornamental crops grown in greenhouses, such as peppers, cucumbers, tomatoes, deciduous plants. Aphidius colemani is especially useful as a tool against pesticide-resistant strains of these aphids.

The host range of Aphidius colemani is more than 41 species.

Aphidius colemani has many positive qualities that often make it one of the first biological control agents introduced by manufacturers.

Under ideal conditions, Aphidius colemani can maintain aphid populations at levels similar to those resulting from the use of pesticides, but in safer conditions and with less application time.

Aphidius colemani has a higher spread rate and search activity than some aphid predators, for example, such as the common Lacewing Chrysoperla rufilabris.

When used in conjunction with predatory aphid midge Aphidoletes aphidimyza in a greenhouse trial, most of the aphid control was attributed to Aphidius colemani.

Aphidius colemani can be grown in a greenhouse on “banker plants”—plants that support a population of non-harmful aphids as an alternative food source for wasps with a low level of aphid pests. This ensures preventive control of aphids, providing a constant source of parasitoid wasps. As an aphid specialist, Aphidius colemani is also compatible with biological control programs against other pests in greenhouses.

When to release?

Aphidius colemani works best with preventive use or when aphids are first detected on crops. This parasitoid moves very quickly 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 release. Broad-spectrum insecticides with long-lasting residual effects should not be used for at least 4 weeks before the release of Aphidius colemani. If several aphid species are present, Aphidius colemani is released together with Aphidius ervi and Aphelinus abdominalis. Also, to achieve better results, it is recommended to introduce additional aphid predators, such as aphid midges and ladybirds.

How to release?

Aphidius colemani 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 rate

The norms will vary depending on the type of target aphid and the level of infection at the time of release. The following coefficients have been determined to control Myzus persicae and Aphis gossypii on greenhouse vegetables and can be used as a guideline.

Preventive: 0.15 / m2 per week.

After aphid detection: 0.5-1/m2 per week for at least 3 weeks. Return to the preventive norm as soon as control is achieved.