A special type of grasshopper (Orthoptera: Acrididae) distinguished by expression of a remarkable and potentially devastating form of phenotypic plasticity, known as density-dependent phase polyphenism.
Changes in local population density cause the development of strikingly different phenotypic forms, or ‘phases’. Low population densities produce the shy, well-camouflaged ‘solitarius’ phase, whereas crowded conditions produce the aggregating, migratory ‘gregarious’ phase.
Solitarious phase locusts avoid one another, but gregarious locusts can form huge groups and embark on spectacular mass migrations, travelling as marching bands of flightless juveniles and vast flying swarms of winged adults. Of the more than 12,000 described grasshopper species, fewer than 20 are considered locusts. Swarming locusts have evolved independently a number of times in a variety of different grasshopper lineages throughout the world. It seems as though a combination of ecological factors has repeatedly favoured the evolution of locusts from their more grasshopper-like ancestors. The relationship between locusts and their environment and how this interaction leads to swarm formation is an active area of research.
Locust of Interest
Locust has been feared agricultural pests since the dawn of civilisation with plagues documented in ancient texts including the Qur’an, Bible and Torah. Locust outbreaks can occur on all of the continents with the exception of Antarctica and have the potential to affect the livelihoods of one in ten people on the planet. A single locust swarm can contain billions of insects and travel hundreds of kilometres each day. On occasion, they can even cross oceans, as happened most recently in 1988 when Desert locust swarms from West Africa flew across the Atlantic Ocean and reached the New World. For these reasons alone, locust biology has long been the object of intense scientific study, to try to find ways to control them.
Locust swarms devastate crops and cause major agricultural damage and attendant human misery—famine and starvation. They occur in many parts of the world, but today locusts are most destructive in sustenance farming regions of Africa. The desert locust (Schistocerca gregaria) is notorious. Found in Africa, the Middle East, and Asia, they inhabit some 60 countries and can cover one-fifth of Earth’s land surface. Desert locust plagues may threaten the economic livelihood of one-tenth of the world’s humans. A desert locust swarm can be 460 square miles in size and pack between 40 and 80 million locusts into less than half a square mile. Each locust can eat its weight in plants each day, so a swarm of such size would eat 423 million pounds of plants every day. Locust swarms can fly up to 150 kilometres a day with the wind, and adult insects can consume roughly their own weight in fresh food per day. A small swarm eats as much in one day as about 35,000 people.
Locust in South Asia
Nibbling their way across a large part of Africa is the worst outbreak, locust swarms are now threatening South Asian countries with India taking extra measures to ward off a new outbreak that could ravage crops. India is buying drones and specialist equipment to monitor the movement of locusts and spray insecticides.
Earlier this year, Indian authorities were able to bring swarms of desert locusts under control, but an outbreak in neighbouring Pakistan has again raised concerns about the safety of crops such as wheat and oilseeds in India.
Pakistan has declared a national emergency to battle the swarms of desert locusts which are eating crops on a large scale and raising fears of food insecurity. Villages in India’s western states of Gujarat and Rajasthan states, which share a border with Pakistan’s desert areas, are especially susceptible to the locust invasion.
COMMON NAME: Locusts
SCIENTIFIC NAME: Acrididae
GROUP NAME: Swarm
AVERAGE LIFE SPAN: Several months
SIZE: 0.5 to 3 inches
WEIGHT: 0.07 ounces
Combatting the Locust Army
To scare away the locusts, communities in Africa make loud noises, blowing whistles and banging pots. But the most effective way to get rid of the pests – and importantly, to prevent their eggs from hatching – is through the ground and aerial pesticide spraying. In Kenya, the UN’s Food and Agriculture Organization and the Ministry of Agriculture are carrying out these measures. But in Somalia, conflict and insecurity make aerial spraying nearly impossible. On February 2, the government of Somalia declared a national emergency, which means the situation has overwhelmed its capacity to respond.
Pakistan’s government declared a national emergency in February in response to swarms of desert locusts in the eastern part of the country. Prime Minister Imran Khan made the emergency declaration following a government briefing on the situation in the first week of February. The information minister of Pakistan stated that the nation is facing the worst locust infestation in more than two decades and have decided to declare a national emergency to deal with the threat. National Food Security Minister of Pakistan Makhdoom Khusro Bakhtiar said the locust swarms were on the Pakistan-India border around the Cholistan and were previously in Sindh and Balochistan, Pakistani newspaper Dawn reported. The minister added the locust attack is unprecedented and alarming. He further said, action has been taken against the insect over 0.3 million acres (121,400 hectares) and aerial spray was done on 20,000 hectares. District administrations, voluntary organizations, aviation division and armed forces are put into operation to combat the attack and save the crops.
India is buying drones and specialist equipment to monitor the movement of locusts and spray insecticides to ward off a new outbreak that could ravage crops, government officials of India said. Earlier this year, Indian authorities were able to bring swarms of desert locusts under control, but an outbreak in neighbouring Pakistan has again raised concerns about the safety of crops such as wheat and oilseeds in India. Other than ensuring the availability of large quantities of insecticides, India is buying drones and sprayers to beef up the readiness to deal with the attack.
With locusts attacking standing crops in different parts of the country and at least three other neighbouring states, Pakistan has proposed setting up a high-level technical committee, comprising senior officers from Southwest Asian countries for effective management and control of the threat. This was suggested during a high-level ministerial meeting organized by the Food and Agriculture Organisation (FAO) of the United Nations (UN) and its Commission for Controlling the Desert Locust in South West-Asia (SWAC). The meeting had been held following requests from four FAO member countries, including Pakistan, Iran, India, and Afghanistan. Pakistan was represented by Federal Food Security Ministry Makhdoom Khusro Bakhtiar, National Disaster Management Authority (NDMA) Chairman Lt General Muhammad Afzal, National Food Security and Research Secretary Dr Hashim Popalzai and other key technical staff from Pakistan. Ministers and senior officials from Iran, India and Afghanistan and key FAO experts in Rome and Pakistan attended the moot. Bakhtiar gave an overview of Pakistan’s action plan to control the locust threat. He proposed the formation of a high-level technical committee, comprising senior officers from Southwest Asian countries, for effective management and control of the locust threat.
Quickies Vs Crawlies
Chinese authorities have dispatched the 100,000 birds to its Xinjiang border in the far west of the country, where it meets Pakistan and India as the locusts continue to swarm eastwards. A trial will take place in the coming months, after which the squadron will be sent to Pakistan’s Sindh and Punjab provinces, as well as the Balochistan province where Chinese experts undertook a field visit to take samples and speak to local agriculturists. Ducks can eat more than 200 locusts a day, compared with chickens which can manage just 70.
Action Plan for Bangladesh
As other neighbouring countries have been severely affected by the monstrous hoppers, Bangladesh needs to create a strategy which can be executed with the existing resources. The farmers need to be warned and at the same time trained to face this crisis, because proper preparedness is the only measure we have against a calamity we have not yet faced, and it could be any day that the locusts swarm into our neck of the woods.
At the time of writing the article, the situation remains extremely alarming in the Horn of Africa, specifically Kenya, Ethiopia and Somalia where widespread breeding is in progress and new swarms are starting to form, representing an unprecedented threat to food security and livelihoods at the beginning of the upcoming cropping season.
KENYA: Hopper bands continue to develop and form an increasing number of first-generation immature swarms in northern and central counties. Further concentration is expected in Marsabit and Turkana. Aerial and ground control operations continue.
ETHIOPIA: No new information received. Hopper bands continue to form within a widespread area of Oromiya and SNNPR regions, including the Rift Valley. A new generation of immature swarms are likely to have started forming in some areas. Aerial and ground control operations continue.
YEMEN: Hopper bands forming on the southern coast near Aden where control was carried out. The situation is not well known in other areas where breeding is likely underway.
IRAN: Swarms and adult groups continue laying eggs in the southwest (southern Khuzestan, Busherh, southern Fars, western Hormozgan provinces). Hatching and band formation imminent. Local breeding continues in the southeast where hoppers are forming groups and bands in eastern Hormozgan. Control operations are in progress.
The situation is under control in the following countries:
SUDAN: Two immature swarms appeared on the southern coast of the Red Sea on the 14th. Scattered adults along parts of the coast.
ERITREA: Conditions drying out on the central and northern coast. Control operations continue against groups of late instar hoppers and immature adults on the Buri Peninsula and in the Dahlak Islands.
EGYPT: Late instar hopper groups treated at one place on the Red Sea coast in the southeast.
SAUDI ARABIA: Control operations against one mature swarm and groups of laying adults near the Persian Gulf between Al Hofuf and Kuwait and a few mature groups in the northern interior south of Al Jawf.
OMAN: Hatching on the north coast and control operations against early instar hopper groups, and continue against late instar hopper groups on the east coast.
LOCUST AIMING FOR BANGLADESH?
Bangladesh has been alerted to keep watch on probable locust infestation, which the country has never experienced over the last five decades. An official of Bangladesh’s Department of Agricultural Extension (DAE) who oversees the affairs of the Plant Protection Wing told a news daily that they have been observing the locust situation closely as swarms of locusts already started invading crop fields in some parts of India and Pakistan. Bangladesh has never experienced locust invasion before. But this year a record infestation of locusts is reported.