locust study may lead to better pest control

Locusts eat voraciously with an appetite that extends to members of their own species. Now scientists have discovered an “anti-cannibalism” pheromone that the insects use to protect themselves in dense swarms, which could pave the way for new pest control strategies.

Scientists said the discovery raises many possibilities, including spraying crops with something like the defense pheromone as a non-toxic insecticide, or finding a way to reduce its impact among locusts and put them on each other more.

“You could make the locusts behave more cannibalistically and they could regulate themselves that way,” said Bill Hansson, director of the Department of Evolutionary Neuroethology at the Max Planck Institute and senior author of the research.

Cannibalism is widespread in nature. “Humans have developed ethical rules that prevent us from being cannibals, but this is not the general rule in nature. For other species, meat is meat,” Hansson said. “A fox will eat a dead fox, a rat will surely eat another rat, a mouse will eat another mouse.”

He said: “In the case of locusts, people think they live off grass and greens, but they clearly eat each other very clearly.”

Migratory locusts exist for most of their lives in a “single phase”; living alone, staying in one area and shying away from other insects. However, when the population density in an area increases beyond a certain threshold, locusts transform within hours into a “large stage”; changing color, becoming very active, aggressive and voracious eaters, and finally it creates a very destructive collective knives that eat everything in its path – including, sometimes, each other.

Scientists have previously shown that cannibalism plays a vital role in Swarm formation as individuals try to eat those in front of them, and avoiding being eaten by those approaching from behind, the Swarm begins to move as one.

The latest work, published in Science, shows that locusts also release a pheromone called phenylacetonitrile (PAN), which keeps cannibalism in check, potentially allowing the swarm to get bigger and feed itself. longer. In a series of experiments, the researchers found that as the number of locusts living in a cage increased, they began to release more of the chemical.

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When the scientists used Crispr genome editing to create locusts that could not produce the PAN enzyme, these insects were more likely to be eaten. And locusts engineered without the ability to smell the pheromone were more likely to eat their fellow insects.

In one experiment, two locusts – one normal, one engineered not to produce the pheromone – were released into a cage of 50 hungry locusts. “The poor guy who didn’t smell just threw it,” Hansson said.

Professor Iain Couzin, of the Max Planck Institute for Animal Behaviour, in Germany, who was not involved in the latest study, said the results were important because locust plagues are expected to have an impact, through their impact on crops , the livelihood of one in ten people. people on the planet.

Couzin said: “Finding a chemical signal that blocks this, as in this work, provides a way to control swarm movements. Insecticides are usually targeted at those species that are beneficial to humans, such as pollinators. This discovery may allow the development of control agents in the future that target molecular pathways specific to plague locusts.”

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