Aphids can weaken our plants so much that they die. We reveal which beneficial insects help against aphids in the garden and how to use ichneumon flies, lacewings, and other insects specifically against aphids.
Aphids (Aphidoidea) are frequent but mostly uninvited guests in our gardens, greenhouses, or even on the windowsill. The plant sapsuckers are only a few millimeters in size and are green to black in color depending on the species.
While they feed on the phloem juice of the plant, they excrete so-called honeydew, which can be recognized as a sticky, shiny coating on leaves. A further characteristic of aphids is the curling of leaves and reduced growth of the plant as a result of the sucking activity.
We introduce you to the most important beneficial insects against aphids in order to take ecological action against aphids.
Which Beneficial Insects Help Against Aphids?
The parasitic wasp and the ladybug are certainly the best-known representatives of beneficial insects that can be used against aphids. But lacewings and gall midges can also help you if your plants are infested with aphids.
Especially for plants in greenhouses, winter gardens, and for indoor plants, beneficial insects can be acquired and settled. In the field, it is recommended to create habitats in which beneficial insects feel comfortable so that they migrate by themselves. It is not so easy to establish them in the field, as the beneficial insects are often simply distributed in the environment and do not remain on the treated plant.
Ichneumon Flies Against Aphids
Some ichneumon flies (Ichneumonidae) parasitize aphids, which offers a very good possibility for natural control. The female lays eggs in aphid larvae or adult aphids, thus suppressing her host, the plant pest.
Both outdoors and indoors, ichneumon wasps can be used against aphids. One female ichneumon wasp can parasitize about 500 aphids in a short time. Here the female lays an egg with her spine into the aphid, which was previously stunned by the ichneumon fly.
The larva hatching later from the egg then kills the aphid. The few millimeters large ichneumon wasp is completely harmless for plants and humans. These beneficial insects against aphids can be purchased on the Internet or in specialized stores in small containers. These containers are hung on the aphid-infested plant and the little helpers distribute themselves.
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The use of ichneumon flies is possible from a temperature above 15 °C. Before use, the aphid species should be determined or a mixture of different ichneumon flies should be used. A particular ichneumon flies species can only parasitize a few aphids. However, the suppliers of ichneumon flies will be glad to advise you.
Ichneumon flies can also help against whiteflies, codling moths, and cabbage whiteflies. If you don’t want to do without the help of ichneumon flies in the open air, you can offer a living space in the form of little wooden trunks with holes a few millimeters in size.
Here you will find the most important aphid species and the matching ichneumon flies:
|Aphid species:||Ichneumon flies:|
|Peach aphid (Myzus persicae)||Aphidius colemani|
|Green cucumber louse (Aphis gossypii)||Aphidius colemani|
|Potato aphid (Macrosiphum euphorbiae)||Aphidius matricariae|
|Black bean aphid (Aphis fabae)||Lysiphlebus testaceipes|
Ladybug Against Aphids
The seven-point ladybug (Coccinella septempunctata) is known by many as a lucky charm – and it also helps us against aphids. The ladybug only feels comfortable in the open air. Although the adult animal also likes to eat aphids, the blue-black ladybug larvae, which are three to nine millimeters in size, are much more voracious.
A single larva can kill up to 4000 aphids within two weeks. Thus, the use of ladybug larvae against aphids is well suited for a strong infestation. You can order ladybug eggs in small containers on the Internet, which you then distribute on the infested plant in the evening or when the sky is cloudy.
At a temperature of 15 to 20 °C, the voracious larvae soon hatch out of the eggs. If you would like to settle the beneficial insects against aphids in your garden, you can promote this with natural hedges and native plants like the white goosefoot.
Lacewings Against Aphids
The larvae of the lacewings (Chrysoperla carnea) are also called “aphid lions” because of their hairy appearance and also like to eat aphids. In the field and in the greenhouse, lacewings can be used against aphids. With their suction tongs, they grab the aphids and suck them out.
One lacewing larva can kill up to 800 aphids within two weeks. The beneficial insects against aphids can be used outdoors, in greenhouses, or in living rooms. You can use lacewing larvae already at temperatures above 10 °C. You can purchase the larvae on the Internet embedded in corrugated cardboard and distribute them on the infested plant with a light tap.
The lacewing is the ideal beneficial insect if your plant is infested not only by aphids but also by thrips or spider mites since the lacewing larvae also love to eat them.
The lacewing will feel especially comfortable in your garden if you offer natural hedges and leave the autumn leaves over winter. You can attract lacewings with a red painted box, in which they find shelter at the same time.
Gall midges (Aphidoletes aphidimyza) are only suitable for use against aphids in greenhouses or living rooms. The gall midge larvae stun the pests and suck them out. One larva can suck out up to 80 aphids within one week. The earlier the beneficial insects are used against aphids, the more effectively they are reduced.
They can be used at temperatures above 18 °C between March and September. Occasional spraying of the plant with water also helps to colonize the gall midge larvae. The larvae and adult animals are completely harmless to plants and humans. Gall midge pupae can be ordered on the Internet, from which the orange larvae hatch. The pupae are placed on the ground under the infested plant.
Predatory Mites Against Aphids
Predatory mites are ideal for combating infestation by spider mites or thrips, for example. However, if your plants are infested with aphids, the use of predatory mites will not be successful. Aphids are not on the diet of predatory mites, which is why we recommend the use of the beneficial insects presented so far.
How To Fight Aphids With Beneficial Insects
Some beneficial insects can be purchased and settled in an acute infestation. But if you want to prevent too many pests, such as aphids, from multiplying too much, you should welcome and preserve beneficial insects in your garden. You can do this with a flower meadow that not only looks beautiful but also provides food for insects.
Especially in summer, our gardens can become very dry, which can be a problem for the insects living there. Here insect watering can help. A small bowl of water and small pieces of cork or wood floating on the water surface gives the insects the opportunity to drink.
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It is also important to use only insect-friendly plant protection measures. Small places of retreat such as accumulations of wood and bark or abandoned withered perennial stems also help to promote beneficial insects in your garden. An insect hotel is also a good idea – it gives the beneficial insects shelter and the opportunity to reproduce. In this way, you not only keep pests at bay, but you also encourage insects that help pollinate your plants.