Explained: How desert locusts made its early arrival to India and how serious would it

New Delhi, May 29: Many know that desert locusts, also known as Schistocerca Gregaria, normally live and breed in desert regions. It is during this time, they require bare ground to lay eggs. With this keeping in mind, these locusts can breed in Rajasthan but not in the Indo-Gangetic plains.

As how the desert lands are required for the locusts, green vegetation is also required for the swarm's development. As individuals, or in small isolated groups, these locusts are not very dangerous. But when they grow into large populations their behaviour changes, they transform from 'solitary phase' into 'gregarious phase'. It is estimated that a single swarm can contain 40 to 80 million adults in one square km, and these can travel up to 150 km a day.

Generally, these locusts breed in the dry areas around Ethiopia, Somalia, Eritrea along the eastern coast of Africa, a region known as the Horn of Africa. Similarly, other breeding grounds are Asian regions in Yemen, Oman, southern Iran, and in Pakistan's Balochistan and Khyber Pakhtunkhwa provinces.

Recently, the Locust Warning Organisation, a unit under the Agriculture Ministry, spotted these and warned of their presence at Jaisalmer and Suratgarh in Rajasthan, and Fazilka in Punjab near the India-Pakistan border.

Why are these locusts arrving early when July-October is the normal time?

It is reportedly said that unusual cyclonic storms of 2018 in the Arabian Sea is the key reason behind these locusts early arrival. Cyclone Mekunu and Luban had struck Oman and Yemen respectively that year. Also, heavy rains had transformed uninhabited desert tracts into large lake where a swarm of locusts could breed. If this issue is left attended, a single swarm can increase 20 times of its original population in the first generation itself. Once they start breeding, the locust swarm movement will cease or slow. Also, the breeding will happen mainly in Rajasthan.

What are the damages they have caused so far?

Since the rabi crop has already been harvested, and farmers are yet to start kharif sowings. However, the UN Food and Agriculture Organization (FAO) has predicted "several successive waves of invasions until July in Rajasthan with eastward surges across northern India right up to Bihar and Odisha". After July, there would be westward movements of the swarms that would return to Rajasthan.

A single gregarious female locust can lay about 60-80 eggs three times during its average life cycle of 90 days. If their breeding is coterminous with that of the kharif crop, we could well have a situation similar to what maize, sorghum and wheat farmers of Kenya, Ethiopia and Somalia experienced in March-April.

How can the population of these pests be controlled?

Locust control has involved spraying of organo-phospate pesticides on the night resting places of the locusts. Recently, the Indian Institute of Sugarcane Research, Lucknow, advised farmers to spray chemicals like lambdacyhalothirn, deltamethrin, fipronil, chlorpyriphos, or malathion to bring things under control. However, On May 14, the Centre had banned the use of chlorpyriphos and deltamethrin. Malathion is also included in the list of banned chemicals but has been subsequently allowed for locust control.