Context: Recently, scientists at the Locust Warning Organisation (LWO) observed groups of grasshoppers at Sri Ganganagar and Jaisalmer districts of Rajasthan.

The Locust Warning Organisation(LWO)  is a part of the Union Agriculture Ministry’s directorate of plant protection, quarantine & storage and with its field headquarters at Jodhpur in Rajasthan.

 Why a new concern?

  • Unlike ordinary hoppers, these were desert locusts - the same destructive migratory pests currently devouring acres of maize, sorghum and wheat crops in East Africa.
  • While locusts are seen in India normally during July-October and mostly as solitary insects or in small isolated groups. 
  • The locusts being spotted along the India-Pakistan border before mid-April this time and coming after the damage they caused to the growing rabi crops along western Rajasthan and parts of northern Gujarat has raised the alarm bells, and comes at a time when the country is battling the more high-profile COVID-19.
  • Genesis of the present locust upsurge(particularly in East Africa)
    • It lies in the Mekunu and Luban cyclonic storms of May and October 2018 that struck Oman and Yemen, respectively. These turned large desert areas of the southern Arabian Peninsula into lakes, allowing the insects to breed undetected. 
    • Widespread rains in East Africa in late March and April have enabled further breeding.
    • Climate conditions as drivers: In the past three years there was an increase in the frequency of cyclones in the Indian Ocean that played a role in breeding this current upsurge.

The map below, from the UN Food & Agriculture Organization, shows areas of locust presence and projections for their movement.

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About locusts:

  • Locusts are a collection of certain species of short-horned grasshoppers in the family Acrididae that have a swarming phase.
  • The desert locust (Schistocerca gregaria) is a short-horned grasshopper that is not harmful while it is in a solitary phase and moving about independently. 
  • These winged insects differ from normal hoppers, and become dangerous only when their populations build up rapidly and the close physical contact in crowded conditions triggers behavioural changes. 
  • Then they enter the gregarious phase, by grouping into bands and forming swarms that can travel great distances (up to 150 km daily), while eating up every bit of vegetation on the way. 
  • If not controlled at the right time, these insect swarms can threaten the food security of countries. 
  • Kenya is already reporting its worst locust outbreak in 70 years, while Ethiopia and Somalia haven’t seen one this bad in quarter of a century.

The kind of damage they cause:

  • Locusts are polyphagous, i.e. they can feed on a wide variety of crops and have an ability to multiply rapidly. 
  • The damage potential of locusts has been limited in India only because of the country hosting a single breeding season - unlike Pakistan, Iran and East Africa, where they also multiply during January-June.

What can be done:

  • If the monsoon is good, and in the absence of control operations, the magnitude of attack could be worse than in the 2019-20 rabi season. 
  • Local authorities in Rajasthan and Gujarat had to treat infested areas with sprayers mounted on tractors and other vehicles. 
  • Even old generation organophosphate insecticides such as Malathion are effective against locusts. 

Control operations also require procurement of equipment, training of field teams, prepositioning of supplies in key breeding areas and updating contingency plans.