The beneficial insects can be used as a natural method of combating plant pests. We reveal how to successfully use parasitic wasps against aphids, whiteflies & co.
Parasitic wasps (Ichneumonidae) are beneficial insects that live as parasites. They lay their eggs for development in insects or insect larvae, causing them to die after the larvae hatch. As soon as all the host insects have been killed, the parasitic wasp is no longer able to stay where it is and it disappears almost unnoticed. This makes it an elegant and ecological alternative to chemical crop protection. But the use of parasitic wasps should be well prepared: the useful little helpers are very specific when it comes to the choice of their host. However, you should not be put off by the high host specificity. Most providers of parasitic wasps also provide comprehensive advice and will help you make the right choice. We will tell you in which areas and how exactly you can use parasitic wasps.
Parasitic wasps are a very species-rich family of insects. Due to the large number of different species, parasitic wasps can also be used against various pests. They prove useful against both aphids (Aphidoidea) and scale insects (Coccoidea) and whiteflies (Aleyrodoidea), better known as whiteflies. They can be used both in closed rooms such as greenhouses or living rooms and outdoors. In closed rooms, the little helpers do not migrate so quickly, which is why their use is particularly effective here. Ichneumon wasps can be used at air temperatures of 15 to 30 °C. Therefore, its use is only recommended from late spring.
parasitic wasps against aphids
Aphids belong to the group of plant lice (Sternorrhyncha) and are annoying companions in every garden. With their stinging mouthparts, aphids suck on the plant's phloem sap, which is very sugary. However, the aphids cannot fully utilize all the sugars in addition to the other valuable phloem componentsuse. Therefore, they excrete most of the sugar as honeydew. This will cause a sticky, shiny film on leaves or your windowsill.
The parasitic wasp is inconspicuous at around three millimeters long, but very effective against aphids. A female can parasitize around 500 aphids in a short time. She uses her sting to lay an egg in the previously stunned aphid. A larva then grows out of the egg, which kills the aphid as it grows - what is known as an "aphid mummy" remains.
If the aphid infestation is very widespread, the parasitic wasps are even able to track down individual animals and to parasitize, which is why they also have a preventive character in the fight. However, if you have problems with a very dense infestation, it is advisable to bring in other beneficial insects such as ladybirds (Coccinellidae).
Note: Some aphid species are "milked" by ants, meaning that the ants use the aphids' sugary honeydew for their own win nutrition. In order to protect their "herd of aphids", the ants defend their aphids against enemies such as the parasitic wasp. Some species of parasitic wasps, for example Lysiphlebus testaceipes, can imitate the smell of aphids by excreting scents, so that they are camouflaged and are not attacked by the ants.
Here is a brief overview of the most important aphid species and their respective most effective opponents:
| Aphid species | Parasitic wasp to control |
|---|---|
| Pea aphid (Acyrthosiphon pisum) | Praon volucre |
| Green peach aphid (Myzus persicae) | Aphidius colemani |
| Big raspberry aphid (Amphorophora idaei) | Praon volucre |
| Potato aphid (Macrosiphum euphorbiae) | Aphidius matricariae |
| Greater rose aphid (Macrosiphum rosae) | Aphelinus abdominalis |
| Black bean aphid (Aphis fabae) | Lysiphlebus testaceipes |
Tip: Ichneumon wasps are sold in the egg stage. The beneficial insect eggs, which are cultivated on a large scale, are applied to cardboard or small paper beads and are therefore immediately ready for application. The shippingtakes place only between 5 and 30 °C and is reasonably only carried out on a few fixed days of the week in order to always guarantee fresh parasitic wasps. The fact that you may have to wait longer for your little animal can therefore be a sign of quality! As soon as the beneficial insects have arrived, you should let them out of their packaging as soon as possible. In any case, we recommend handling the little helpers carefully so as not to crush them. Please also note: Depending on the severity of the infestation and the room situation - i.e. outdoor, conservatory or greenhouse - a repeated order at intervals of two weeks is necessary to permanently decimate the plant lice.
parasitic wasps against scale insects
Scale insects (Coccoidae) attack your plants, particularly by sucking out the plant sap. The males are usually winged and appear as solitary individuals. The females of most species, however, have a eponymous flat and shield-shaped body. The females of the scale insects (Coccidae) have a very strongly arched back and therefore have a rather spherical body. Mealybugs (Pseudococcidae), also known as mealybugs, also belong to the group of scale insects, but instead of the shield-shaped body they have conspicuous white "hair" made of wax threads. Female scale insects live in colonies and diligently suck on the phloem of the plant. They also lay their eggs under their shield on the leaves of the infested plant, from which new adult pests later develop.
Because the scale insect family includes many different species, it is important to choose the right pest control helpers. The parasitic wasp Metaphycus flavus, for example, feeds on eggs and young scale insect nymphs. She also lays eggs under scale insect nymphs, from which parasitic wasp larvae hatch. These penetrate the pest and help you get rid of the scale insects. In turn, new beneficial insects develop in the parasitized cocoons. The parasitic wasp species with the greatest success in controlling scale insects is Metaphycus flavus. But other parasitoid species such as Coccophagus lycimnia and Aphytis melinus are showing good results.
Important: If you have trouble accurately identifying the small parasites, vendors of beneficial insects offer support. The host specificity of beneficial insectsis the determining factor whether a fight is crowned with success or not.
parasitic wasps against whitefly
The term "white fly" does not actually mean a fly, but a trivial name for some representatives of the whitefly (Aleyrodidae). The main pests referred to as whitefly are the diamondback whitefly (Aleurodes proletella) and the greenhouse whitefly (Trialeurodes vaporariorum). Whiteflies are one to two millimeters in size, their wings are covered with white wax dust. The larvae of the pest are particularly feared in greenhouses, but can be brought under control by using beneficial insects. Due to the spatial limitation, the parasitic wasps are prevented from migrating to other hosts and can therefore be used in a very targeted manner. It is important that the temperature in the greenhouse is optimal. Depending on the parasitic wasp species, the ideal temperature is between 18 and 22 °C and is crucial for the development of the parasitic wasp population. By airing them regularly, you can ensure that the little helpers feel comfortable.
The parasitic wasp species Encarsia formosa has proven to be particularly valuable with regard to whitefly control. It is doubly useful: Older developmental stages of the larvae are parasitized and serve as hosts for the growing next generation of Encarsia formosa. Young developmental stages are used as food by adult parasitic wasps.
Summary: Using parasitic wasps against plant lice
- Parasitic wasps can be used against various plant lice, namely aphids, scale insects and whiteflies.
- Parasitic wasps only parasitize certain lice, which is why you should make sure that the parasitic wasp matches the pest when using it in a targeted manner. Beneficial traders will be happy to advise you on this.
- It can be used indoors and outdoors, although it is much more effective indoors.
- The air temperature should be between 15 and 30 °C for successful use.
- Temperatures between 18 and 22 °C and regular airing ensure that the parasitic wasps stay he althy and busy.
Alternative control method: pest-free neem
In case of a heavy infestation with whiteflies, scale insects or aphidsHouseplants are sometimes not enough for beneficial insects such as parasitic wasps. The targeted use of beneficial insects is often difficult in the wild, too. In these cases we recommend the use of a biological pesticide. Such biological pesticides protect the naturally occurring beneficial insects in the field, which means that they can continue to "work for you" as a preventive measure instead of being harmed. Unfortunately, this does not usually apply to synthetic plant protection products against plant lice. You should make sure that you do not use beneficial insects and pesticides at the same time, including biological agents.
Neem-based preparations are a very effective way of naturally combating aphids, scale insects or whiteflies. The neem oil from the seeds of the neem tree contains the active ingredient azadirachtin, which is ideal for use against plant lice. Our Plantura organic pest-free neem is based on this valuable neem oil and offers you a way to combat pests using purely plant-based methods. The active substance is taken up by the lice when sucking on the plant and causes a quick stop of the sucking activity. The development of the larvae is disturbed, so that the entire population is damaged and disappears. Plantura organic pest-free neem is simply mixed with water and the emulsion is sprayed onto the affected plant. You can find precise information on the dosage and use of Plantura organic pest-free neem on the product packaging. You can use organic pest-free neem both indoors and outdoors - it is not dangerous to bees. Please note that you use our organic pest-free neem as specified in the application recommendation. Therefore, please read the package insert before use.
Tip: Plantura Organic Pest Free Neem not only works excellently against aphids, scale insects and whiteflies, but also helps you to fight spider mites naturally.
You can find more exciting information about "Fighting aphids" in our special article.