Nematodes Information

 What are nematodes?

Nematodes are microscopically small (0.6 to 1 mm), unsegmented worms that occur naturally in the soil throughout the world.

Are there different types of nematodes?

Yes, there are entomopathogenic nematodes (insect parasitic), plant pathogenic nematodes, and saprophytic nematodes. The entomopathogenic nematodes are natural enemies of a lot of insects.

 Are all nematode species harmless?

No. Plant pathogenic nematodes cause harm to plants. However, entomopathogenic nematodes are 100% safe for plants, animals and humans. This is because only insects can be host to this group of nematodes. By far the most nematodes belong to the group of saprophytes. These nematodes are harmless and live of dead organic matter to provide a rich soil life.

 How do entomopathogenic nematodes work?

Nematodes are actively looking for a host or using an ambush strategy to reach their host. Once in contact with a host, they try to penetrate it through a body opening. In the host, the nematodes release a bacterium that can kill the host very quickly. This bacterium also causes the host to be converted into food for the nematodes. This food enables the nematodes to complete their life cycle.

 Are there different types of entomopathogenic nematodes?

Yes. The most common entomopathogenic nematodes belong to the families Heterorhabditis or Steinernema. In addition, there are a number of other families and species, but they are found in much smaller quantities.

 Are the released bacteria harmful?

No. This group of bacteria is only harmful to insects and cannot survive outside an insect or in warm-blooded organisms.

 Can entomopathogenic nematodes overwinter (temperate climate)?

No. Nematodes cannot survive at very low temperatures and certainly not outside a host. Only if the nematode is in the host and the temperature is not too low is there a small chance that the nematodes can overwinter. However, this is never to the extent that enough nematodes are available in spring to be able to have a sufficiently controlling effect.

 Do entomopathogenic nematodes work at all stages of the pest insect?

It depends. Some pests are susceptible to nematode infection in both larval and adult stages, some only during the larval stages (and some only as adults). As a general rule, nematodes have a preference for targeting young larvae, especially in the case of large insects.

Do entomopathogenic nematodes only work as a soil application?

Most are dedicated to soil pests but for several above ground pests foliar applications show good efficacy, provided the fields/greenhouses offer the optimal temperature and humidity conditions required. For instance, nematodes can be used against palm tree pests, caterpillars, thrips, Nesidiocoris, asparagus beetle, Tuta absoluta and several fruit moths and beetles…

How do I apply nematodes?

Nematodes should be applied with water. Once resuspended in water, the nematode suspension can be broadcast using the most common spraying/irrigation systems in agriculture and gardens: a watering can, backpack sprayer, pump sprayers, Airblast sprayers etc. They can also be delivered via drip irrigation systems with a preference for high pressure. Remove filters if finer than 0.3 mm.

 What pressure can be on the pump sprayers?

The pressure on the nozzle may not exceed 20 bar (190 psi), with conventional large volume nozzles.

 Why should the soil be wet before/after treatment?

Nematodes are sensitive to drought. When they are introduced into a dry substrate/soil they will die. Also when the soil dries out very quickly after application. In addition, they use moisture in combination with soil particles to move. Dispersion is not possible without a water film.

How long after application should the substrate remain moist?

As long as the soil is not dry, the nematodes will survive and search for a host. It is therefore important to leave the soil moist for a few weeks after application of nematodes.

Can I apply nematodes to each substrate/soil?

No. In particular in clean rock wool slab they cannot maintain well and they will flush with the drain. (Pot) soil, on the other hand and if not too dry, is always good.

When can I expect effect? How fast do the nematodes work?

Under optimum conditions, a nematode can kill an insect in 24-48 hours. Under practical conditions, a nematode will first have to look for a host. The effect of treatment is thus strongly dependent on how quickly a nematode has found a host.

Is the effect visible? 

Infected larvae will change color because of the growth of the bacteria and nematodes. In case of Heterorhabditis pink-reddish and Steinernema yellow-brownish. Under practical conditions, infected insect larvae will quickly become slimy and thus will no longer be found. In practice, the decrease of pest pressure is the only indication that the application has been effective.

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