Locust invasions are dramatic and sudden — and they destroy everything green that comes in their way. The swarms that made way into India in 2019 caused large-scale devastation to crops and general vegetation.
The unprecedented behaviour of desert locusts is a cause of concern, for India is facing the worst locust attack in about 27 years.
Heavy rains triggered the growth of vegetation in arid areas of southern Iran and southwest Pakistan where locusts then grew and bred. These locusts migrated to India in early 2020 and found greener pastures due to pre-monsoon rains in March-May.
Locust are short-horned grasshoppers, some species of which under favourable climatic conditions congregate, move together as bands and swarm over long distances crossing over countries and continents rapidly, stripping fields and enormously damaging crops.
They take rapid advantage of the climate and geography, survive in temperature range of 0-60 degrees Celsius and prolong or cut short their life cycle.
A solitary locust actively avoids contact. But under favourable conditions, particularly after heavy spells of rain, the contact becomes unavoidable. As the insects bump into one another, they begin to change — in an hour or so, they become attracted to each other.
During the course of one or two successive generations, they change in shape and colour to become bold yellow from the neutral brown.
Cyclones Mekunu (May) and Luban (October) of 2018 hit the Arabian Peninsula and caused unusual spell of rain in the deserts of Somalia, Oman and Yemen. Extended humid conditions gave rise to favourable breeding conditions for locusts for almost nine months, which remained undetected and hence, uncontrolled.
The locust bred successfully for three generations in such favourable conditions, increasing in numbers that even the local ecosystem could not hold the population. In such conditions, the locust population started to look for new areas for feeding and breeding.
In January 2019, the first swarms of locusts left the Empty Quarter desert to Yemen, Saudi Arabia and southwest Iran. From February to June 2019, widespread spring breeding in Yemen, Saudi Arabia and Iran led to the formation of a large numbers of swarms. But control operations were largely unsuccessful in Iran and Yemen.
During June-December 2019, swarms invaded the Indo-Pakistan border from Iran; up to three generations grew in the summer breeding in India.
Owing to the three cyclones in the Arabian Sea — Vayu (June 10-17), Hikaa (September 22-25) and Kyarr (October 24-November 1) — and early monsoon rains, widespread rains took place between June and November, particularly in locust-infested areas.
These extended rains created excellent breeding conditions and led to the development of lush green vegetation in Rajasthan and Gujarat, on which the locusts could feed. The monsoon did not retreat by September-October and lasted a month longer.
The locusts came to Jaisalmer, Rajasthan, by end-May and bred for three generations instead of one. In October, more locust swarms arrived from the west and laid eggs that upon getting congenial environmental conditions, developed into pink swarms.
These swarms then started to infest crops in Rajasthan and Gujarat in December 2019-January 2020 as most green vegetation in the desert area had dried out by the time these locusts developed into adults.
Combating strategies: Short-term measures
A robust approach by the Union government agencies and various departments of states is required for effective desert locust control. Locusts are most vulnerable when they are in the hopper stage.
To minimise environmental damages, pesticides, which are active for a short time, should be used. It gets difficult to control locusts when the adult locusts emerge from the fifth-instar hoppers and mature; they form swarms and fly away. At the same time, farmers should be advised to not take their livestock for grazing in area being sprayed on with pesticide for at least one week.
The Locust Warning Organisation deals with locust crisis in India. As part of the locust control measure, the central government deployed multiple resources and established temporary control camps. Drones will also be used to spray pesticides on tall trees and inaccessible places for effective control of locusts.
Plans to deploy helicopters for aerial spray are afoot. The central government is also procuring 55 vehicles indigenously and 60 sprayers from Micron company of Britain for locust control.
The central government has issued advisories to 15 states and directed them to take necessary measures for effective control.
Directives from the United Nations Food and Agriculture Organisation, which is monitoring the situation on a global scale, should be followed diligently for effective locust control.
India has also proposed a trilateral initiative with Pakistan and Iran for effective locust control. The Indian Meteorological Department should provide the wind pattern data for proper tracking of the movement of locust swarms.
The present situation has been aggravated with the novel coronavirus disease (COVID-19) pandemic. The lockdown has led the world to slip into economic recession.
In such a situation, locust survey and control may be done by strictly following the instructions by the government. Some of them include wearing face masks, hand gloves, personal protective equipment, washing hands, observing social distancing and observing personal hygiene to protect.