Applying pheromones to nematodes turns them into the ultimate natural pesticide, drastically increasing destruction of insects
Introduction
Do roundworms make you squeamish? If so, it’s understandable. They have no eyes, they wriggle unnervingly, and many of the best known species are parasites. There is good reason, though, to check this attitude toward the squirmy creatures.
Nematodes, most less than a millimeter in size, have an extremely simple body plan; it is often said that they are merely a “tube within a tube.”
Infective juveniles (IJs) emerging from a wax moth larva.
The Strategy
A few nematode species have evolved to target insects (weevils, borers, beetles, and moths, just to name a few) that humans deem “pests” because they destroy our crops. Farmers have begun employing them as a natural pesticide––a more environmentally-friendly alternative to chemicals.
Studies have now shown that pheromones called called ascarosides play a key role in triggering the critical dispersal phase of their life cycles, when young nematodes known as “infective juveniles” (IJs) will search through soil until encountering an insect they can infect.
When scientists applied ascarosides to IJs, more of the young nematodes began moving toward their target host, more successfully invaded the host, and more successfully killed the host.
Once inside, the IJs release bacteria that kill the host. They then feed on the body as they grow into adults and reproduce––sometimes for multiple generations. Finally, when every edible shred of the host has been consumed, a combination of chemical and environmental cues brings on the dispersal phase, releasing IJs into the soil to search for a new host and begin the cycle anew.
When scientists applied ascarosides to IJs, more of the young nematodes began moving toward their target host, more successfully invaded the host, and more successfully killed the host.
In an isolated test plot seeded with engorged adult female ticks, parasitologist Dolores Hill sprays infective juvenile Steinernema nematodes as a biological control.
The Potential
Scientists suggest that nematodes could be exposed to these pheromones before being applied to crops for up to 78% more pest-killing efficacy. The company Pheronym is already producing nematode pheromones for commercial use, helping to pave the way toward a more eco-friendly agriculture system.
