EXPLAINED | What are locusts and how are they harmful?

Last Updated 29 May 2020, 10:48 IST

After leaving a devastating trail in Gujarat, Madhya Pradesh, and Rajasthan, swarms of desert locusts have entered the Vidharbha region of Maharashtra, proceeding towards Delhi and Uttar Pradesh.

So you must be wondering what kind of insects these locusts are that are wreaking havoc amidst the ongoing pandemic and how exactly are they harmful? Here is an explainer on the menacing locusts and their behaviour.

What are Locusts?

Locusts have been feared and revered throughout the history. Very closely related to grasshoppers, these insects form enormous swarms that spread across regions, devouring crops and causing serious agricultural damage. They look like ordinary grasshoppers—most notably, they both have big hind legs that help them hop or jump. They sometimes share the solitary lifestyle of a grasshopper, too.

Swarms of locusts have devastated human habitats since the Pharaohs-led ancient Egypt, and they still wreak havoc today. Locusts have been termed as the oldest migratory pests in the world by the Food and Agriculture Organization (FAO), the desert locusts being the deadliest of them all.

Types of locusts

The Desert Locust, the Bombay Locust, the Migratory Locust, the Italian Locust, the Moroccan Locust, the Red Locust, the Brown Locust, the South American Locust, the Australian Locust, the Tree Locust are some of the species of locusts found in the world.

So what are Desert Locusts?

The desert locust (Schistocerca gregaria) is a particularly notorious species of the insect and is one of about a dozen species of short-horned grasshoppers (Acridoidea) that are known to change their behavior and make swarms of adults or bands of hoppers (wingless nymphs). As per National Geographic, found in Africa, the Middle East, and Asia, this species inhabits an area of about six million square miles, or 30 countries, during a quiet period. During a plague, when large swarms descend upon a region, these locusts can spread out across around 60 countries and cover one-fifth of Earth's land surface. Desert locust plagues threaten the economic livelihood of one-tenth of humans.

Do Desert Locust plagues occur with any regularity?

Well, the FAO of the United States or even the Locust Warning Organization of India have not yet found any evidence of the fact that Desert Locust plagues occur after a specific number of years. Instead, plagues develop intermittently. “This kind of rapid and massive attack was witnessed in 1993, nearly 27 years ago. Predicting how many locusts can enter the region is difficult, given the lack of pattern of such incidents and the uncertainty of rainfall in locust areas. So, the solution largely lies in controlling the attack through spraying pesticides,” A M Bharia, Plant Protection Officer from the Locust Warning Organisation, told The Better India.

How are locusts harmful?

So, you must be thinking, how can such tiny, grasshopper-like herbivores pose threats to countries and humans? Well, it is really simple, by eating up crops together in unity.

FAO says that an adult Desert Locust can consume roughly its own weight in fresh food per day, that is about two grams every day. Now, a 1 km size swarm contains about 40 million locusts, which eat the same amount of food in one day as about 35,000 people consume. This comparison is based on a person eating an average of 2.3 kg of food per day, according to the USDA.

The catch here is their ability to reproduce exponentially and then formi swarms. National Geographic notes that, during dry spells, solitary locusts are forced together in the patchy areas of land with remaining vegetation. This sudden crowding releases serotonin in their central nervous systems that makes locusts more sociable and promotes rapid movements and more varied appetite.

National Geographic further explains that, when rains return—producing moist soil and abundant green plants—the environmental condition creates a perfect storm, and then Locusts begin to reproduce rapidly and further increase in number. In these circumstances, they shift completely from their solitary lifestyle to a group lifestyle in what’s called the gregarious phase. Locusts can even change colour and body shape when they move into this phase. Their endurance increases and even their brains get larger.

Which countries are currently affected by locusts?

FAO has been concerned about the “extremely alarming” situation in East African countries, especially in Kenya, Ethiopia and Somalia. There, hundreds of billions of locusts in swarms the size of major cities, are causing damage to the crops in their path. It is the worst outbreak in 25 years in Ethiopia, and in Kenya, it is the worst in seven decades.

Making their way through Africa, locust plagues have now reached Pakistan, Iran, Saudi Arabia, Southern Republic of erstwhile USSR and of course, India.

Why are Desert locusts so hard to control?

After careful study, the FAO has come up with the following reasons as to why desert locusts are so hard to control:

(1) The extremely large area (16-30 million sq. km) within which locusts can be found.

(2) The remoteness and difficult access to such areas.

(3) The lack of safety (such as land mines) in some areas.

(4) The limited resources to monitor locust and control their movement in some of the affected countries.

(5) The undeveloped basic infrastructure (roads, communications, water and food) in many countries.

(6) The difficulty in maintaining a sufficient number of trained staff and functioning resources during the long periods of recession in which there is little or no locust activity.

(7) political relations amongst affected countries.

(8) The difficulty in organising and implementing control operations in which the pesticide must be applied directly onto the locusts.

(9) The difficulty in predicting outbreaks given the lack of periodicity of such incidents and the uncertainty of rainfall in locust areas.

The FAO also estimates that about one million people in the country have already been pushed into hunger by the locust infestation.

How countries are combating the locust crisis amidst the COVID-19 crisis

Even though affected countries are being stretched thin and challenged by the locust plague, it is critical to act now to prevent further devastation and the threat of a multi-year famine.

According to data from the Famine Early Warning Systems Network, the current hotspots of locust activity on the Horn of Africa and Yemen are happening in countries that are already experiencing “stress,” “crisis” and “emergency” levels of food insecurity.

So, to combat this crisis within a crisis, the World Bank Group is moving to provide flexible support to countries affected by the outbreak. The World Bank Group is coordinating closely with partners, including the UN-FAO, which is leading the control efforts.

In India, at present the primary method of controlling Desert Locust swarms is mainly using organophosphate chemicals in small concentrated doses (referred to as ultra low volume (ULV) formulation) by vehicle-mounted and aerial sprayers, and to a lesser extent by knapsack and hand-held sprayers.

Besides the Ministry of Agriculture and Farmers Welfare, the Department of Agriculture, Cooperation and Farmers Welfare, other ministries such as External Affairs, Home Affairs, Defence, Earth Sciences, Civil Aviation and Communications, etc. have also come together in India to help combat this Desert Locust emergency.

(Published 28 May 2020, 11:34 IST)

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