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Chemical signal for locust swarming identified in step toward curbing plagues

A worker from Somaliland's Ministry of Agriculture holds a desert locust after spraying them with bio-pesticide in one of the breeding grounds for the desert locusts in Geerisa town, Lughaya District, some 350km north east of the capital Hargeisa, Somaliland, 05 March 2020 (issued 19 March 2020). According to the United Nations Food and Agriculture Organisation (FAO) despite control efforts the desert locusts have rapidly spread across the Great Horn of Africa in the worst infestation in decades affecting eight countries in Eastern Africa including (Kenya, Somalia, Uganda, Ethiopia, South Sudan, Tanzania, Eritrea and Djibouti). FAO estimates that 20.2 million people are now facing severe acute food insecurity in East Africa region warning that if the desert locust swarms continue unhindered, the population could increase 400-fold by June and the next generation will begin to form swarms from late March and throughout April 2020, which coincides with the start of the next seasonal rains, and also the main planting season for the region. (Photo: EPA-EFE/Daniel Irungu)

WASHINGTON, Aug 12 (Reuters) - Scientists have identified a chemical compound released by locusts that causes them to swarm, opening the door to possible new ways to prevent these insects from devouring crops vital to human sustenance as they have for millennia.

By Will Dunham

Researchers said on Wednesday they identified the pheromone – a chemical produced by an animal that affects the behavior of others of its own species – in the world’s most widespread locust species, the migratory locust, or Locusta migratoria.

Called 4-vinylanisole (4VA), it is primarily released from the hind legs and is detected by the antennae of other locusts and sensed by odorant receptors, the researchers said.

4VA powerfully attracted locusts regardless of age or sex, the research published in the journal Nature showed. Its production was triggered in the insects when as few as four to five solitary locusts came together, precipitating swarming behavior.

“In human history, locust plagues, drought and flood were considered as three major natural disasters which caused serious agricultural and economic losses all over the world,” said research leader Le Kang, a professor of entomology and ecology at the Chinese Academy of Sciences’ Institute of Zoology.

“As the most widely distributed and one of the most dangerous locust species, the migratory locust represents a serious threat to agriculture worldwide,” Kang added.

Swarms can include billions of locusts and span hundreds of square miles (km) as the insects voraciously consume crops, imperiling food security. Migratory locusts inhabit Asia, Africa, Australia and New Zealand, attacking pastures and critical crops such as wheat, rice, corn, millet, barley, oats, sugarcane and sorghum.

Kang said further research is needed on whether 4VA exists in other locust species such as the desert locust, called Schistocerca gregaria, that currently is ravaging parts of Africa and the Middle East.

The chemical insecticides currently used to suppress locust outbreaks raise concerns about human health and safety. The identification of 4VA could inspire new methods.

A chemical could be developed to block 4VA’s effects to prevent swarming, Kang said, or a synthetic version could lure locusts into traps to be killed. Locusts genetically modified not to respond to 4VA could be developed and released to establish wild non-swarming populations, “subject to biosecurity evaluation,” Kang added. (Reporting by Will Dunham; Editing by Sandra Maler)

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