Aphid midge (Aphidoletes aphidimyza)

Aphid midge (Aphidoletes aphidimyza) is a Cecidomyiidae midge whose larvae are effective predators of aphids. The insect represents a family of Cecidomyiidae, and looks like a small gnat with long, thin legs. Initially, a new species was described for each attacked victim, and at least 24 previously described species were identified as Aphid midge. This midge is an important component of biological control programs for greenhouse crops in many countries, due to which it has received wide commercial distribution.

Description

Adult Aphid midge are small, about 2-3 mm, slender insects. They look like gnats, with long thin legs and very long antennae. The eggs are orange, oval and very small (about 0.1–0.3 mm). The larvae initially have the same colour as the egg. During the passage of 3 age stages, they increase in size to 2-3 mm. Depending on the food source, their colour ranges from bright orange to red. The body of the larva characteristically narrows towards the head. Also, the larvae have a well-developed oral apparatus, with which they “grab the victim”.

Habitat (crops):

Greenhouses, homesteads, orchards — potatoes, ornamental plants, berries, etc. In greenhouses, Aphid midge has become indispensable for the control of aphids on perennial vegetable crops. Although very few field introductions have been recorded, studies show that there is potential for aphid control on many crops in the open ground. Aphidoletes aphidimyza has been found on cabbage, apples, blueberries and ornamental shrubs and is recognized as an important natural aphid control agent on Russian and Egyptian cotton.

Victims

Aphidoletes aphidimyza affects more than 60 species of aphids.

Life cycle

The life span of the female imago is 1-2 weeks. During their lifetime, they lay, in groups or individually, about 70 eggs on the leaves of plants on which aphids live.

After 2-4 days, predator larvae are born. The larva attacks aphids, hitting their limbs with a paralysing toxin, after which it sucks out its juices, leaving a blackened, curled aphid on the leaf.

If the concentration of aphids is high, the larvae paralyse more aphids than they are able to eat, killing them. It is recommended to use as an agent suppressing aphid outbreaks, and not as a preventive measure.

One larva needs at least 7 aphids to complete its life cycle, but it can eat up to 80. In addition, the larvae kill more aphids than they can eat.

In the greenhouse, the larvae descend into the soil for pupation less than 1 week after emergence.

Adults appear after 1-2 weeks.

In the field, larvae develop in 1-2 weeks, and pupation can last up to 3 weeks. The life cycle in the field can be from 3-6 weeks. They are capable of producing 3-6 generations per year, largely depending on the length of daylight.

Adult entomophages prefer the dark and fly at night, so they are rarely seen. Imagos feed on dew.

Aphid midge overwinter larvae in cocoons, in the soil, pupating in spring. Adults appear in late spring, mate on the first night after hatching, and the mated females immediately begin searching for aphids. Most eggs are laid within the first few days after the transition to the adult stage.

Effectiveness

Imago Aphidoletes aphidimyza are very effective at detecting aphid colonies. In one study, entomophages detected one infected plant per 75 non-infected. Integrated pest control programs for greenhouse vegetables recommend using these midges, often in combination with the release of parasitoid wasps Aphidius ervi and Aphidius colemani, for more intensive control of aphids.

Larvae are most typically found in the field from mid to late summer. The massively released midges made it possible to adequately control aphids in tests, even on small open household plots.

A short daylight by the end of summer can cause diapause. This can be avoided in the greenhouse by using additional lighting at night. However, since they lay their eggs at dusk, they also need a period of low light in the evenings.

The conditions for optimal operation are 18-25 °C with a relative humidity of at least 70%.

Because they pupate in the soil, it is difficult or impossible to get them to successfully complete their life cycle in hydroponic systems.

Recommendations

A short light day, less than 12 hours, will cause a diapause in the predator, and it will be ineffective. They can be used in hydroponic systems, but due to the lack of soil for pupation, the population will not be established. It is important to control ants before releasing midges or parasitoid wasps controlling aphids. Aphids produce carrion, which is a food source for ants. Because of this, ants protect them from predators and parasitoids. In addition, do not release in combination with the common Chrysoperla, as the larvae of the Lacewing will eat the larvae of the Aphidoletes aphidimyza.