Parasitic wasps

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The parasitic wasps (Ichneumonidae), like bees and bumblebees, belong to the order Hymenoptera (hymenoptera). In Central Europe, there are many different species whose larvae parasitize other insects, including many pests. Therefore, parasitic wasps are important beneficial agents in biological pest control. The Hymenoptera feel especially at forest clearings, at forest edges, in meadows, bushy landscapes as well as in parks and gardens. They feed mainly on nectar, honeydew and bee pollen.

Hybrids are often between five and ten millimeters in size and can reach a length of 0.2 to 50 millimeters, depending on the species. The physique of the animals is characterized by the typically slim "wasp waist". The animals have translucent dark wings and long, movable antennae. Parasitic wasps are often black or dark brown in color and often have red spots or stripes. The male animals of some parasitic wasps resemble the true wasps (Vespinae). Characteristic of parasitic wasps is the so-called Legestachel.

way of life

With their pronounced sense of smell, the female wasps detect the larvae of spiders and insects such as beetles, bees, wasps and butterflies, which they inject their eggs into the body with their long laying spines. However, before laying the eggs, the hymenoptera first inject a toxin with the laying spike into the host in order to paralyze it. After the injection, the larvae hatch inside the host animals and pupate. Insects that have been parasitized are often significantly bloated and brown to black discolored. The larvae feed on their host and eat it from within. To hatch, the young parasitic wasps drill a hole in the back skin of their host after pupating - hence the name of the group of animals stirs.

Close-up of a wasp

Web wasps are extremely useful animals in the garden

The parasitic life of parasitic wasps effectively prevents large crop failures caused by insect pests. Therefore, the beneficials are also used in agriculture specifically as an opponent of many pests. Be sure to leave the parasitized animals on the appropriate plants, as they grow into a new, helpful generation of parasitic wasps. But parasitic wasps can also be attacked by so-called secondary parasitoids or hyperparasitoids. This can severely limit their efficiency. The natural predators of parasitic wasps are also insect-eating birds.

Parasitic wasps as beneficials

For example, parasitic wasps are used selectively in the greenhouse, conservatory or garden for biological and natural pest control. For this purpose, the specialized trade offers specially bred parasitic wasps such as Encarsia formosa, which you can use, for example, against larvae of the white fly and the miner fly. Also for use against the larvae of the killer whitefly, the aphid, the eggs of the European corn borer and the codling moth there are specially bred beneficial species.

Suitable parasitic wasps can be purchased in the garden shop or on the Internet. Usually the parasitic wasp eggs are divided into several deliveries, so that the beneficial insects can be used successfully over a longer period of time. In our latitudes especially the true parasitic wasp (Ichneumonidae), the aphid wasp (Aphidius colemani) and the Brackwespe (Braconidae) are of great importance for biological pest control. The commercially used animals often belong to the genus Trichogramma. This species only reaches a size of a pinhead and is thus particularly small.
Lay out the parasitic wasp eggs on the affected plants as early as possible in order to prevent a pest infestation in time. The approximate guideline is around 50 toothed wasp eggs per square meter in the garden. A parasitic wasp can, for example, kill up to 300 white fly larvae and thus inhibit the multiplication. Aspirin wasps can also be used preventively on cucumber and tomato plants. Here, the beneficials act preventively against pests and parasites.


In closed rooms, for example in a greenhouse, parasitic wasps are particularly effective

The parasitic wasps need a temperature between 20 and 27 degrees Celsius and a humidity of about 60 percent to be optimally effective. In bad conditions, the pests multiply faster than the beneficials - the fight then shows no success. The use of parasitic wasps is very efficient, especially in the greenhouse or indoors, a controlled use in the garden is a bit more difficult, because you can not localize the small animals.

Attract parasitic wasps in the garden

For humans, parasitic wasps pose no danger.Therefore, you can use the useful animals without hesitation in your own garden for natural and biological pest control. A near-natural garden and the absence of toxic and broad-spectrum pesticides make it possible that parasitic wasps spread in the garden in large numbers and you can use their help effectively against pests.
Wasps overwinter partly as larvae or pupae in the mummies of parasitized animals, but also partially as fertilized females in tufts of grass and tree stumps, under moss or a loose tree bark. Since adult parasitic wasps feed mainly on the nectar of garden plants, the animals are particularly attracted to Umbelliferae.


The nectar of umbelliferae attracts parasitic wasps

If you want to keep parasitic wasps in the garden for the long term, you should provide the helpful skinflies with a suitable living space. Drill small holes in a log and place them in your garden. With a little luck, the parasitic wasps settle after some time on their own. Whether an insect hotel is accepted, you can not say in advance unfortunately.

Video Board: Body Invaders | National Geographic.

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