Nematodes: Roundworms As Beneficial Insects In The Garden

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Nematodes act as beneficial insects against many plant pests. But what are nematodes and how do you use them correctly?

Nematodes offer the possibility of biological control of a large number of pests. When using nematodes, however, you should always keep in mind that they are living organisms. We will show you which pests you can use nematodes against and how to proceed correctly. In this article, you will find all the information you need for a successful nematode deployment.

Nematodes: profile, appearance & Co.

Nematodes, which are also known as elk, are transparent to white in color and cannot be seen with the naked eye. So far, over 20,000 different species are known. Depending on the species, nematodes have very different properties. The small roundworms feed on species-specific plants, bacteria, algae, fungi, predatory or dead animals, for example. Many also live parasitically, for example, roundworms, trichinella, and whipworms, all of which also belong to the nematode group.

The nematodes (Nematoda) relevant for crop production are small roundworms that are less than a millimeter in size. Depending on the specialization of food intake, they can be harmful or beneficial to plants. Some species can attack vegetables and other plants as pests. If you have problems with nematodes, our article on nematodes as pests will definitely help you.

Nematodes: roundworms as beneficial insects in the garden

Nematodes as beneficial insects

So what makes some nematodes effective beneficial insects? Roundworms can actively move and spread in the soil. This ability gives the nematodes a greater chance of meeting prey in the garden. Their small size enables the roundworms to penetrate the interior of the pests through body openings and thus kill them. Then they use the pest bodies to multiply. Roundworms have much smaller allies when it comes to pest control: They are special bacteria that live in symbiosis with the nematodes. If a nematode and a suitable prey animal meet, the nematode injects the victim with the bacteria. These then digest the pest from within – the nematode can then use the prey as food and multiply. The nematodes then leave the killed pest and look for a new host. In this way, the nematodes can remain in the soil for months under good conditions.

Another advantage is that the use of nematodes has no negative side effects for your plants or the environment. Incidentally, in almost all cases it is the pest larvae and not the adult pests that are controlled by the nematodes.

The great diversity of nematode species means that many different pests can be attacked, for example:

  • Sciarid gnats
  • Vine weevil
  • Grubs
  • Ants
  • Snails
  • Cherry fruit flies
  • Box tree moth
  • Mole crickets
  • Thrips
  • Wiesenschnaken

Application of nematodes: timing, procedure, and duration of action

For successful use of nematodes, a few points should be observed:

  • Before you can plant nematodes, you must find out what pest it is. Only certain nematodes can be used against various pests.
  • When is the right time in the year to carry out a nematode treatment depends on the pest and the weather? Because if it is too cold or too dry, the nematodes are not active. Since usually only the larvae of the pest in the soil can be combated, the time should be chosen so that the pest is in the larval stage. In the following, we give you the best times to combat the most common pests.
  • The soil temperature must be right for the respective nematode species. If the temperature is too low, the nematodes completely stop their activity. Most species can be used at a soil temperature between 12 and 28 ° C.
  • Nematodes are sensitive to UV light. For this reason, you should avoid spreading the roundworms during the day. The evening or the early morning is better.

Where can you buy nematodes? You can purchase various nematodes on the Internet in specialized shops or using order cards from the garden center. You can also order three different types of nematodes that are effective against the most common pests in our Gardender online shop. You will then receive the nematodes as durable, permanent larvae in a powder that serves as a carrier substance, directly in your mailbox.
To maintain this dormant state, you must store the nematodes in the refrigerator until use. How long you can store the nematodes can be found in the product packaging. Our Gardender nematodes can be stored for up to 6 weeks before use.

What is the correct approach to using nematodes? Mix the powder containing the nematodes with water. The exact mixing ratio can be found in the product packaging. You should moisten the area to be treated well with water before applying the nematodes. The suspension can now be spread evenly on the surface to be treated with a watering can. You can also read the size of this area on the product packaging. After application, you should re-water the treated area with water to flush the nematodes into the soil. While the nematodes do their work, you should make sure that the soil is always moist. However, waterlogging must be avoided at all costs.

Nematodes: roundworms as beneficial insects in the garden

Tip: We recommend using the nematodes for several years in a row for pests with development cycles lasting several years, such as garden beetles or mole crickets.

What about the duration of action of nematodes? You can find the first dead larvae in the soil after just a few days. The introduced nematodes are in the ground for several months under very good conditions, but their number is steadily decreasing. Optimal pest control is only given in the first four weeks after application.

Tip: If, for example, larvae of the black weevil ( Otiorhynchus ) have been successfully attacked and killed by nematodes, they will turn red-brown. In this way, you can check whether the application has worked.

Summary: how to properly apply nematodes

  • The time of treatment depends on the pest and can be found in the package insert.
  • The floor temperature must be permanently between 12 and 28 ° C.
  • Spread the nematodes in the morning or the evening.
  • Mix the purchased powder, including the nematodes, with water.
  • Use the watering can to spread the nematodes onto the moistened soil and then soak them in water.
  • Keep the soil moist for at least two weeks to encourage the nematodes.

Nematodes: roundworms as beneficial insects in the garden

Nematodes against fungus gnats

The adult sciarid gnats (Sciaridae) do not actually damage any plants. However, the larvae of the sciarid gnats stay in the ground and feed, among other things, on young roots. In this way, the larvae can harm the plants. House plants in particular are often attacked by fungus gnats. We have put together helpful tips on how to fight sciarid gnats in our article.
The nematode species Steinernema feltiae (SF nematodes) has proven itself against fungus gnats. Steinernema feltiae can be used on indoor plants all year round and outdoors from a soil temperature of 12 ° C. We present our Gardender SF nematodes in more detail on this page.

In the event of severe infestation or if you want to be on the safe side, we recommend combining it with a biological agent-based on neem oil. Our Gardender organic fungus gnat-free neem enables you to get naturally rid of fungus gnats.

Nematodes against black weevils

Black weevils, or more precisely their larvae in the soil, can be controlled by nematodes. HB nematodes can be used to protect rhododendrons ( Rhododendron ), ivy ( Hedera helix ), hydrangeas ( Hydrangea ), and other plants from the dreaded bay weevil eaters. The nematode species Heterorhabditis bacteriophora can be applied from a soil temperature of 12 ° C and is used for reliable and biological control of the black weevil. We recommend using our Gardender HB nematodes between April and Mayor, alternatively, between August and September.

Nematodes: roundworms as beneficial insects in the garden

Nematodes against grubs

Grubs are the larvae of scarab beetles such as June beetles ( Amphimallon solstitial ), cockchafer ( Melolontha melolontha ), or rose beetles (Cetoniinae). They can cause damage if they multiply in mass on lawns. The complete and permanent control of white grubs can sometimes take years for the stubborn larvae – especially for the cockchafer. The reason for this lies in the many larval stages of the grubs, not all of which are susceptible to the effects of pesticides
A biological possibility of control is the use of HB nematodes against cockchafer, junior beetle, and rose beetle larvae. Since only the first two young stages of development of the grubs are effectively controlled, the time of control is very important, as is the right type of nematode: Heterorhabditis bacteriophora can be used between July and September against grubs of junk beetles, garden beetles, and somersaults.

Nematodes against ants

Ants are actually not pests and are part of a healthy garden. But if they get out of hand on patios or paths, control may be necessary. In this case, you can use our Gardender SF nematodes of the species Steinernema feltiae, just as with sciarid gnats. The nematodes disturb the ants so that they leave the treated area together with their brood.

Nematodes: roundworms as beneficial insects in the garden

Ants can be a nuisance, especially in the house. We recommend that you use a biological agent when combating ants in your home. A particularly harmless agent for humans and animals is, for example, our Gardender ant remedy InsectoSec®, which uses pure diatomaceous earth as an active ingredient.

Nematodes against snails

As every amateur gardener knows, nudibranchs can cause significant damage in the garden. You can also use nematodes to fight snails. The particular advantage: snails multiply particularly rapidly in damp weather. The nematodes also need moist conditions to develop well.
So that the fight against snails is effective, you should use the nematode species Phasmarhabditis hermaphrodite. The optimal floor temperature is between 12 and 25 ° C. Another advantage is that the harmless snails and house snails are spared.

Roundworms against other pests

The nematode Steinernema feltiae is not only effective against fungus gnats and ants but also the larvae of the cherry fruit fly. However, the effect is not nearly as good as that of the fungus gnat. The cherry fruit fly larvae can only be combated at the moment when the larvae migrate from the infected cherry into the ground. Therefore, the nematodes must be applied to the soil in such a way that they are actively present in the soil during this time. A good time to do this is in early June.

To be able to use nematodes against the box tree moth, the nematodes must be integrated into a certain wetting agent. Only in this way do they come into direct contact with the larvae of the box tree moth.
The nematode species Steinernema carpocapsae is suitable for combating the box tree moth. You will find precise information on the correct application on the product packaging. The optimal treatment time is two weeks after you have discovered the first adult animals. To determine this point in time, we recommend a moth trap.
For effective and environmentally friendly control of the box tree moth, we can also recommend a remedy based on the living Bacillus thuringiensis. One such agent is, for example, our Gardender borer-free XenTari®.

Nematodes: roundworms as beneficial insects in the garden

Too large many mole crickets (Gryllotalpidae) can be very annoying in the vegetable patch. The nematode species Steinernema carpocapsae can be used against mole crickets. Here the adult animals are attacked and killed. The optimal period for control is between March and July with a soil temperature of 12 ° C.

Meadow snakes can be a problem, especially on lawns. Biological control against meadow snakes is possible with our Gardender SC nematodes. The larvae of the meadow snake are killed by the nematode Steinernema carpocapsae. The optimal control date is around two weeks after the meadow Schnake flight height, between September and October.

Nematodes can also be used against thrips (Thysanoptera). The flowering thrips ( Frankliniella occidentalis ) is one of the most common species and is a particular problem in greenhouses or living spaces. Steinernema feltiae attacks the pupa of the flowering thrips and kills them. The control can therefore take place all year round.

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