Nematodes: an asset in the fight against caterpillars

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Nematodes: an asset in the fight against caterpillars

13 July 2021

Parasitic nematodes have traditionally been an important tool in the fight against soil infestations. However, they also appear effective when applied to the leaves. The nematodes combat caterpillars and other insect larvae, even in situations where other methods have ceased to work.
Parasitic nematodes are so small that they penetrate caterpillars and larvae with ease. They occur naturally in the ground and so it makes perfect sense to start using them for soil infestations. ‘We have been doing this since 1986. They are great for dealing with the pupae and larvae of thrips, the larvae of vine weevils and several beetles, caterpillars, the larvae of sciarid flies and many others,’ Product Manager Cyrille Verdun explains.
How did it prove possible to ‘train’ soil-living organisms for use on leaves? Verdun continues: ‘It comes down to three words – test, test, test. We carried out tests to find out which types of nematode were most suitable and what the right conditions were. We constantly tested improved formulations and tried to identify the best approach for each infestation.’

Nematode-bacteria interplay
In many crops, the caterpillar problem is getting worse – there’s Tuta absoluta for example, and the oak processionary caterpillar. Parasitic nematodes are by no means fussy eaters. ‘The approach works on many insect orders,’ he explains.
Especially on insect orders such as Coleoptera larvae or Lepidopteran larvae (caterpillars). Once inside the host, the nematodes release bacteria which are responsible for the dirty work, poisoning the caterpillar before killing it and dissolving the tissue into a nutritive soup. This soup feeds the nematodes, which continue to grow, reproduce, and then leave the dead caterpillar in search of the next victim.

The right conditions
Under the right conditions, nematodes can survive on the leaf for several days, all the while seeking out new caterpillars or larvae. ‘You need to be kind to them. They love humid air conditions (>70% relative humidity) and an optimum temperature between 14 to 32°C. But they can start working from 10°C and even withstand cold shock down to 5°C for several hours. There’s usually a microclimate between the leaves, which offers just the right level of humidity. It’s also important for the leaf to be well covered, which can be achieved with wetting agents and adherents. Spraying in the evening when there’s minimal sun irradiation is the way to achieve the best result. You can find videos on the Koppert YouTube channel that explain exactly what you need to do,’ explains the product manager.

IPM and nematodes
Parasitic nematodes work well within an Integrated Pest Management system. The initial growers have since had positive experiences using parasitic nematodes against stubborn infestations such as caterpillars. They can also be used to control the nymphs of bugs such as Nesidiocoris. ‘You need to be careful that they don’t also attack the larvae of some other beneficials, but the results show that collateral damage of this kind is rare if you remain mindful of it and phase in the use of the various beneficials,’ Cyrille Verdun explains.
It’s also important to know that nematodes are safe for humans. Another advantage is that nematodes are relatively resistant to pesticides, thus opening up the possibility of using integrated methods. If in doubt, consult the Koppert side effects app.

Entonem and Capsanem.
Koppert has two products for leaf application – Entonem with the nematode Steinernema feltiae and Capsanem, containing Steinernema carpocapsae. Below 15°C, Entonem is the best choice, while Capsanem is better at higher temperatures.

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