Locust attack

About locust:

Locusts are the oldest migratory pest in the world which is mainly tropical grasshopper with strong powers of flight.
They differ from ordinary grasshoppers in their ability to change behaviour (gregarize) and form swarms that can migrate over large distances.
The most devastating of all locust species is the Desert Locust (Schistocerca gregaria).

Characteristics of locusts:

Locusts have a high capacity to multiply, form groups, migrate over relatively large distances (they can fly up to 150 km per day) and, if good rains fall and ecological conditions become favourable, rapidly reproduce and increase some 20-fold in three months.
Locust adults can eat their own weight every day, i.e. about two grams of fresh vegetation per day.
If infestations are not detected and controlled, devastating plagues can develop that often take several years and hundreds of millions of dollars to bring under control with severe consequences on food security and livelihoods.

Preconditions for its growth:

Desert locusts (Schistocerca gregaria), which belong to the family of grasshoppers, normally live and breed in semi-arid or desert regions.
While for laying eggs, bare ground is required, green vegetation is required for hopper development. (Hopper is the stage between the nymph that is hatched from the eggs, and the winged adult moth.)
Locusts are not very dangerous as individuals, or in small isolated groups, but when they grow into large populations their behaviour changes, they transform from ‘solitary phase’ into ‘gregarious phase’, and start forming ‘swarms’.
A single swarm can contain 40 to 80 million adults in one square km, and these can travel up to 150 km a day.
Large-scale breeding happens only when conditions turn very favourable in their natural habitat, desert or semi-arid regions.
Good rains can sometimes generate just enough green vegetation that is conducive to egg-laying as well as hopper development.

Reason for this year’s locust attack:

There are two meteorological drivers behind the current locust invasions:

- Many of the usual breeding grounds of locusts received unusually good rains in March and April, and that resulted in large-scale breeding and hopper development.
- These locusts started arriving in Rajasthan around April, much ahead of the normal July-October normal.
- Breeding places: dry areas around Ethiopia, Somalia, Eritrea along the eastern coast of Africa, adjoining Asian regions in Yemen, Oman, southern Iran, and in Pakistan’s Balochistan and Khyber Pakhtunkhwa provinces.

- Locusts are known to be passive flyers, and generally follow the wind. Their movement has been aided by westerly winds that were, this time, further strengthened by the low pressure area created by Cyclone Amphan in the Bay of Bengal.

When July- October is the normal time, how did they arrive so early?

Unusual cyclonic storms of 2018 in the Arabian Sea

Cyclonic storms Mekunu and Luban had struck Oman and Yemen respectively which resulted in heavy rains that had transformed uninhabited desert tracts into large lakes where the locust swarms breed.

Reason for eastward movement of swarms:

Immature locusts in search of food:

The current swarms contain “immature locusts” which feed largely on vegetation.
They consume roughly their own weight in fresh food every day, before they become ready for mating.
With no crops in the field in Rajasthan, they have been invading green spaces, including parks, in Jaipur and orange orchards near Nagpur.
Once they start breeding, the swarm movement will cease and also, the breeding will happen mainly in Rajasthan.

So, what damage have they caused?

Since the rabi crop has already been harvested, and farmers are yet to really start kharif sowings it didn’t cause much damage.
The UN Food and Agriculture Organization (FAO) has, however, predicted several successive waves of invasions until July in Rajasthan with eastward surges across northern India right up to Bihar and Odisha.
But after July, there would be westward movements of the swarms that will return to Rajasthan on the back of changing winds associated with the southwest monsoon.
The danger is when they start breeding because a single gregarious female locust can lay 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 have a situation similar to what maize, sorghum and wheat farmers of Kenya, Ethiopia and Somalia experienced in March-April.

Control measure:

A proactive exercise of control, through aerial spraying of ultra-low volume of concentrated insecticides in all potential breeding sites, is required, along with continuous monitoring of the crops during the ensuing kharif season.

Pesticides used:

Historically, 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 control the swarms.
However, the Centre had banned the use of chlorpyriphos,deltamethrin and Malathion but Malathion has been subsequently allowed for locust control.

Who warns?

The Food and Agriculture Organisation (FAO) provides information on the general locust situation to the global community and gives timely warnings and forecasts to those countries in danger of invasion.
Locust Warning Organisation (LWO), Directorate of Plant Protection Quarantine and Storage, Ministry of Agriculture & Farmers Welfare, Department of Agriculture, Cooperation & Farmers Welfare is responsible for monitoring, survey and control of Desert Locust in Scheduled Desert Areas mainly in the States of Rajasthan and Gujarat.
The LWO monitors, forewarns and controls locust in the Scheduled Desert Area, conducts research on locusts and grasshoppers, keeps cooperation and coordination with National and International Organizations and undertakes HRD through training and demonstration.

About FAO

The Food and Agriculture Organization of the United Nations (FAO) is a specialized agency of the United Nations that leads international efforts to defeat hunger and improve nutrition and food security.

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