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Locust plague explained: Why locusts are being sighted in urban areas, what it can mean for crops

Locust Attack: Over the last few days, swarms of locusts have been sighted in urban areas of Rajasthan, which is unusual. Why are locusts being seen in urban areas? What led to their early arrival?

Written by Parthasarathi Biswas | Pune | Updated: May 29, 2020 2:47:08 pm
locust, locust attacks, locust attacks jaipur, locust attacks rajasthan, locust attack crops, locusts attack farmers, indian express A swarm of desert locusts in Jaipur on Monday. (Express Photo: Rohit Jain Paras)

Over the last few days, swarms of locusts have been sighted in urban areas of Rajasthan, which is unusual. Swarms have also been reported from parts of Madhya Pradesh and Vidharbha region of Maharashtra. The first swarms were sighted along the India-Pakistan border on April 11, months ahead of the usual time of arrival.

What are locusts and when are they are sighted in India?

The desert locust (Schistocerca gregaria) is a short-horned grasshopper. Innocuous when solitary, locusts undergo a behavioural change when their population builds up rapidly. They enter the ‘gregarious phase’ by forming huge swarms that can travel up to 150 km per day, eating up every bit of greenery on their way. These insects feed on a large variety of crops. If not controlled, locust swarms can threaten the food security of a country. At present countries in the Horn of Africa such as Ethiopia and Somalia are witnessing one of the worst locusts attacks in the last 25 years.

In India, locusts are normally sighted during July- October along the Pakistan border. Last year, parts of Western Rajasthan and Northern Gujarat reported swarms that caused damage to growing rabi crops. These were the first swarms reported in India since 1997. This year, the first sightings of small groups were reported early — on April 11 — by scientists of the Agriculture Ministry’s Locust Warning Organization (LWO), from Sri Ganganagar and Jaisalmer districts of Rajasthan.

Maharashtra to step up vigil against locusts in border districts A desert locust. (Reuters Photo: Feisal Omar)

Why are locusts being seen in urban areas?

Locusts are being seen in areas not historically associated with such sightings — Jaipur, MP’s Gwalior, Morena and Sheopur, and recently stray swarms in Maharashtra’s Amravati, Nagpur and Wardha.

K L Gurjar, Deputy Director of LWO, said there being no crops in the fields, the locusts have moved across states attracted by green cover. “The swarms were aided by high-speed wind and thus they made their way to Jaipur,” he said. At present there are three to four swarms in Rajasthan, another two or three in Madhya Pradesh, from where a small group has migrated to Maharashtra, which Gurjar said would not be very difficult to control.

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Explained: Why locusts are being sighted in urban areas, what it can mean for crops The desert locust (Schistocerca gregaria) is a short-horned grasshopper. (Express Photo: Rohit Jain Paras)

Keith Cressman, senior locust forecaster of the UN Food and Agriculture Organization said the locusts have started moving in search of food. “Spring-bred swarms from Pakistan started arriving in Rajasthan earlier this month. As this is before the monsoon rains, they found dry conditions so they continued to move east in Rajasthan looking for green vegetation for food and shelter where they will mature and then lay eggs with the onset of the monsoon in about five weeks,” he said.

What led to their early arrival?

This can be traced back to the cyclonic storms Mekunu and Luban that had struck Oman and Yemen respectively in 2018. These turned large deserts tracts into lakes, facilitating locust breeding that continued through 2019. Swarms attacking crops in East Africa reached peak populations from November, and built up in southern Iran and Pakistan since the beginning of 2020, with heavy rains in East Africa in March-April enabling further breeding.

Explained: Why locusts are being sighted in urban areas, what it can mean for crops In India, locusts are normally sighted during July- October along the Pakistan border. This picture is from Jaipur, on Monday. (Express Photo: Rohit Jain Paras)

What can it mean to crops in India?

At present, chances of crop damage are low given that farmers have already harvested their rabi crop. Orange growers in Maharashtra have expressed concern but as Gurjar said, the swarm in Maharashtra would be easy to control.

The bigger problem will come once the present swarms breed. An adult female locust lays 80-90 eggs thrice in her three-month life cycle. If left uncontrolled, a swarm can grow exponentially to 40-80 million locusts per square kilometre, Gurjar and others estimatee. The locusts will start laying eggs after the monsoon starts and continue breeding for two more months, with newer generations rising during the growth phase of the kharif crop.

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Explained: Why locusts are being sighted in urban areas, what it can mean for crops If not controlled, locust swarms can threaten the food security of a country. (Express Photo: Rohit Jain Paras)

Earlier this month, Union Agriculture Minister Narendra Singh Tomar chaired a meeting to take stock of the situation. Control involves spraying insecticide on locusts’ night resting places like trees. Till date, the LWO has carried out spraying over 21,675 hectares in Rajasthan. India has also put an order of 60 specialised insecticide sprayers with the UK. Gurjar said the country already has 50 such machines. “Also, drones will be used to spray the resting places,” he said.

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