Locust swarm signal identified in step towards curbing plagues

Scientists say discovery of chemical compound that triggers locust swarms offers new ways to stop them

Lochom Ekiru, a 65-year-old farmer from Turkana, assesses the severe damage of his maize crops after locusts ravaged them in Kalemngorok, Turkana County, Kenya. All Photos by AFP

A Turkana farmer try to shoo away locust damaging her maize crops in Kalemngorok, Turkana County, Kenya. An increasing number of second-generation immature swarms of desert locust continue to form in northwest Kenya.

Turkana farmer Joseph Tirkwel asses the damage to his crops

A farmer points at a cluster of locusts.

A farmer holds up a crop with locust devouring maize.

Members of Kenya's NYS -National Youth Service prepare tp spray pesticides to kill the swarms of locusts.

Members of Kenya's NYS -National Youth Service prepare tp spray pesticides to kill the swarms of locusts.

A man sprays around a wooded area.

A man pesticides in a farm in Nakukulas, Turkana County, Kenya.

Spurred by favourable weather conditions, the migratory pests have descended on East Africa in record numbers since late 2019.

Another wave is about to take to the skies despite the concerted use of pesticides.

The World Bank in May approved a $500 million (Dh 1.8 billion) programme to help countries vulnerable to hunger in East Africa fight the pests eating their way across the region.

In Kenya, where swarms blotted out the sky for miles in recent months, locusts have retreated to just three semi-arid counties in the country's far north.

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

Researchers said on Wednesday they identified the pheromone – a chemical produced by an animal that affects the behaviour 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 behaviour.

"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 Kang Le, 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," Dr Kang said.

Swarms can include billions of locusts and span hundreds of square kilometres as the insects voraciously consume crops, imperilling food security. Migratory locusts inhabit Asia, Africa, Australia and New Zealand, attacking pastures and critical crops such as wheat, rice, corn, millet, barley, oats, sugar cane and sorghum.

Dr Kang said further research is needed on whether 4VA exists in other locust species, such as the desert locust, Schistocerca Gregaria,which 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, Dr 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", Dr Kang said.