Description

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Picture Courtesy: THE HINDU

Context:

Researchers have shown the possibility to manipulate pheromones released by locusts to prevent them from swarming or engaging in group behaviour that leads to the feeding frenzy

What are locusts and why do they swarm?

Locusts are a type of grasshopper. Their ability to change from being solitary (living alone) to becoming gregarious (living in large groups) makes them unique and dangerous.

When locusts enter their gregarious phase, they form huge swarms. These swarms are extremely destructive.

The UN Food and Agriculture Organization estimates that a swarm of about 40 million locusts (which covers about 1 square kilometer) can eat as much food in a single day as 35,000 people. They eat thousands of hectares of crops in just days, leading to massive food shortages and economic losses.

Most recently, in 2019-2020, a record-breaking number of locusts emerged in East Africa and traveled through Pakistan and India, causing the worst infestation in the region in 25 years.

What is "pheromone"?

It is a chemical signal that an animal releases into the environment. Other animals of the same species detect this signal and react to it in specific ways, affecting their behavior.

Researchers from the Institute of Zoology at the Chinese Academy of Sciences in Beijing showed that they can manipulate the pheromones released by locusts. This manipulation can prevent locusts from swarming or engaging in the group behavior that leads to their destructive feeding frenzies.

How do locusts change from solitary to swarming?

4VA Release => After a solitary locust eats food, it releases large amounts of 4VA from its hind legs.

Attraction => The 4VA acts as an "aggregation pheromone," quickly attracts other locusts of the same species when it spreads through the air.

Physical Contact => Locusts attracted by 4VA begin to gather closely. They start rubbing their hind legs against each other.

Serotonin Release => The physical contact triggers the release of a chemical called serotonin (a neurotransmitter, which is a brain chemical that sends signals).

Swarming Begins => The release of serotonin then leads directly to the locusts starting to swarm.

How did researchers figure out how to block the swarming signal?

Identifying the Trigger => They discovered that locusts only release 4VA after they eat. This suggested that certain molecules in the plants locusts eat might be triggering the 4VA production. They found that a common compound in plants called phenylalanine was the culprit.

The Enzymes => When locusts digest phenylalanine, two specific enzymes—mainly 4VPMT1 and 4VPMT2—are responsible for converting a harmless chemical (called 4VP, which is present in solitary locusts) into the swarming pheromone 4VA.

The researchers "deactivated" (turned off) the gene responsible for creating the 4VPMT1 enzyme. When they did this, the locusts stopped changing from their solitary phase to their gregarious (swarming) phase and did not show any signs of wanting to swarm.

Locust control strategy proposed by the researchers

Step	Description
1. Attract and Trap	Use synthetic 4VA or other similar compounds to lure locusts to specific trapping areas.
2. Targeted Elimination	Once trapped, eliminate the locusts at a small, localized scale using fungal pathogens (like biopesticides) or very limited amounts of chemical pesticides.
3. Prevent Aggregation	Spray small amounts of 4VA in areas where swarming is likely to begin to confuse the locusts and prevent them from forming large, destructive groups.
4. Population Monitoring	Continuously monitor locust populations by tracking the presence and intensity of 4VA chemical signatures in the environment.
5. Genetically Modified Locusts (Future)	Release genetically modified locusts into the field. These modified locusts would not be able to produce 4VA (because their 4VPMT genes are turned off), thus establishing non-gregarious populations that do not swarm.

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Spotted Locusts II Locust infestation II Ecology and Impact

Source:

THE HINDU

PRACTICE QUESTION

Q. Consider the following statements about "locust":

1. All locusts are short-horned grasshoppers, but not all short-horned grasshoppers are locusts.

2. The Desert Locust is considered the most destructive migratory pest.

Which of the above statements is/are correct?

A) 1 only

B) 2 only

C) Both 1 and 2

D) Neither 1 nor 2

Answer: C

Explanation:

Statement 1 is correct: Locusts are a specific group of short-horned grasshoppers in the family Acrididae that have the ability to change their behavior and morphology to form swarms. While all locusts are a type of grasshopper (specifically, short-horned grasshoppers), most grasshopper species do not exhibit this swarming behavior and thus are not classified as locusts.

Statement 2 is correct: The Desert Locust (Schistocerca gregaria) is widely recognized as the most destructive migratory pest in the world due to its ability to form dense, highly mobile swarms that consume vast amounts of crops and forage. A single square kilometer swarm can contain up to 80 million adults and consume the same amount of food in one day as 35,000 people.