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Some say nematodes, others know them as roundworms. This name was deliberately chosen, because it is paper-thin animals that are not visible to the naked eye. But even if these nematodes are very small and inconspicuous, they can really help the garden owner effectively.
The advantage: nematodes multiply very quickly and are therefore ideally suited for use in the garden against plant pests. How can the nematodes help me? Very easily. They play a major role in the formation of humus and also eat algae, fungi and bacteria. Often, they even use the latter bacteria to tackle enemies such as snails, which are also considered the most common pests.
In addition to the snails, nematodes can also be used to control weeping weevils. These are beetles, which feed mainly on buds and leaves and are therefore not very nice to the garden owner. But do not worry: the nematodes kill the weevil and its larvae. Nematodes also occur against garden gadwall beetles, mole crickets and gnats. As far as their function. But where do you get these animals?
The purchase is not a problem, you can conveniently order the beneficials on the Internet or you go to the gardening market of your trust. Nematodes like to get wet, so they should be put in water and spread out on the floor of the garden, where they will start working.
The temperature should be at least 12 degrees if you use the beneficials, otherwise they can not survive. Incidentally, certain types of nematodes can also occur as pests. Then they suck on roots or they eat parts of leaves or buds. Therefore, be sure to inform yourself in advance so that there are no malfunctions in the garden and the nematodes become your friend and not enemies. Let us advise you in detail and individually for your garden by an expert.
Nematodes against black weevil
The larvae of the Fringed weevil (also known as the White-toothed weevil) are one of the typical root pests of garden and potted plants, while the adult is responsible for leaf-eating. Black-eared weevils (genus Otiorhynchus) belong to the family of weevils (Curculionidae), the largest domestic beetle family. Many weevils appear as pests and are intensively fought accordingly. They are easily recognized by the forwardly extended head, which is pulled out like a trunk and carries the antennae.
The larvae of the Frayed Black-weevil are legless, yellowish-white and have a brown head capsule. However, this applies to a whole series of beetle larvae, so that the identification is not easy.
The animals are easier to recognize by the damage they leave to plants: while adult beetles eat semicircular serrated bays in leaf margins, the larvae infest the roots of the host plant from their roots. As a result of heavy infestation, the plant wilts or dies, mild infestation is reflected in delayed or halting growth.
In agriculture, too, Otiorhynchus sulcatus causes enormous damage. Above all, vineyards, strawberry fields and nurseries are affected.
Adult beetles are susceptible to various pesticides, but can also be collected by hand on a small scale. The larger problem is the larvae, which are now being used successfully to fight nematodes.
Nematodes are relatively pristine, simple-built worms, which prefer to occur in damp to wet soils where they can reach extremely high density. Many species are also regarded as root pests, but some as beneficials.
At least three types of nematodes are currently available to control Otiorhynchus:
Heterorhabditis bacteriophora penetrates into the beetle larva and infects it with a bacterium (genus Photorhabdus), which proliferates rapidly within a very short time. The beetle larva dies as a result of the infection within a few days. H. bacteriophora feeds on the bacteria and in turn multiplies in the host larva. The young worms finally leave the dead host and go in search of the next larva. Prerequisite for the use of H. bacteriophora is a soil temperature of at least 10-12° C
At soil temperatures below 12° C, the nematode Steinerma kraussei be used. The way of life is the same as in H. bacteriophora, but the species is more tolerant of lower temperatures and can therefore be used from February to November.
To combat adult beetles are nematodes of the species Steinerma carpocapsae used. These are supplied as a bait trap in a gel substrate. When the beetles visit the trap as a hiding place, they become infected with the nematodes.The principle is again the same as the other two types
Acquisition and application
Nematodes, like many other beneficial organisms, can also be ordered online. The delivery usually takes place as a powder, which is mixed with water immediately before use and then applied to the affected areas with the watering can.
The packaging should be opened immediately before use. If this is not possible immediately after receipt, the nematodes can be stored at 8-12° C for a few days. If you want to spread the beneficial organisms in very dry places, you should pre-wet the soil and make sure that during the working time the soil is kept moist. Otherwise, the animals retreat into deeper soil layers or dry up.
The Steinerma bait trap consists of a board that is laid out under the infested shrub or tree. Again, the soil should be sufficiently moistened. The board must also be kept moist to prevent the substrate from drying out.
The effects of beneficial organisms are not as fast as those of pesticides, so some patience is needed. In addition, you should take action at an early stage as soon as pest infestation is recorded, because at some point, the beneficial insects can no longer effectively control a pest infestation.