Nematode worms trials could help develop sustainable pest controls

NUI Maynooth trials on nematode worms could give Irish agri-food an edge in the global drive to develop sustainable pest controls.

These tiny worms’ killer instincts are usually directed by males at rival males in their own gene pool. However, the NUIM trials show that this instinct may also be used against horticulture pests such as pine weevil and vine weevil, potentially replacing chemical pesticides.

“There are two sides to our trials with these worms,” said NUIM biology lecturer Dr Christine Griffin. “One side is our study of their behaviour towards other insects. The other side is how this can be applied in the agriculture sector as an alternative to using chemicals.

“They are simple animals, but their behaviour can be quite complex. We are trying to understand their decisions and their behaviour to help us target them more efficiently in terms of their use as a pest control.”

Farmers will be familiar with ‘bad’ nematodes that attack their plants, including root-knot nematodes and eel worms. The nematodes in the NUIM trials function more as an ally to bacteria.

These nematodes squeeze rivals to death when they feel their genetic dominance is under threat. The researchers are looking at how they seek out rivals.

“They are already being used against vine weevils in horticulture, ornamentals and mushrooms,” said Dr Griffin. “We are using them in forestry to control the pine weevil. They are being used, but mostly in niche markets because they are more expensive than chemical pesticides. They are a more sustainable option, and that will become an increasingly important focus for the industry.

“Our trials look at the question of how one worm can kill another. When we understand their natural behaviour we can target them more effectively.”

The Maynooth researchers have tied the male worms’ back to overcrowding at a juvenile stage in their development. This arrested development leads directly fighting in adults. “Nematodes may be simple animals, but many of the biochemical and neural processes that take place in them have parallels in higher animals including humans,” said Dr Griffin.

“Fighting, let alone fatal fighting, has not previously been described in any other nematode. Fighting to the death is relatively rare amongst animals.”

Coillte Teoranta are working on the worm trials with Dr Christine Griffin, PhD student Annemie Zenner and their research colleagues at NUIM.

In nature, worms kill insects and reproduce inside the insect cadavers. Several generations can pass through a large insect and, eventually, tens of thousands of nematode descendants emerge from the spent cadaver in soil and wriggle away in search of fresh hosts. These researchers’ work suggests these are the kind of conditions where the fatal fighting is most likely to evolve.

Killing is a feature of the first colonists that enter the insect, but not of the worms of subsequent generations that develop later inside the insect. For worms of later generations, there would be too many competitors (and many of them close relatives) to make fighting a profitable course of action.


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