Locust

Primary reference(s)

FAO, 2009. Glossary on Desert Locust. Food and Agriculture Organization of the United Nations (FAO). Accessed 10 October 2020.

Additional scientific description

Locusts are defined as belonging to a large group of insects commonly called grasshoppers which are recognisable by the large, thickened hind legs that are used for jumping. All grasshoppers belong to the superfamily Acridoidea, and the most significant species are all in the family Acrididae. Locusts differ from grasshoppers in that they have the ability to change their behaviour, physiology, colour and shape (morphology) in response to changes in their population density. The life cycle of all species of locusts and grasshoppers comprises three stages: egg, hopper, adult (FAO, 2009a).

A plague of locusts is defined as a period of one or more years of widespread and heavy locust infestations, the majority of which occur as bands or swarms. A plague can occur when favourable breeding conditions are present and control operations fail to stop a series of local outbreaks from developing into an upsurge that cannot be contained. A major plague exists when two or more regions are affected simultaneously (FAO, 2009a).

The Desert Locust (Schistocerca gregaria) is able to fly long distances and migrate very fast. It is a transboundary pest, whose control requires international collaboration. This is also the case for about a dozen other locust pests, which can produce outbreaks on every continent except Antarctica (FAO, 2015).

The Desert Locust is considered the most dangerous migratory pest in the world to threaten crop production and food security. It might be the oldest registered pest for its danger and ability to live and breed under wide-ranging ecological and climatic regimes, in vast areas covering 29 million km2 and extending from the Atlantic Ocean in the west to India and Pakistan in the east (FAO, 2009a). During plagues, swarms can invade more than 60 of the world’s poorest countries, and potentially damage the livelihood of one tenth of the world’s population, mostly in Africa, the Middle East and Asia (FAO, 2015).

The worst Desert Locust outbreak in decades is currently underway in the Greater Horn of Africa Region (FAO, 2020a). Tens of thousands of hectares of cropland and pasture have been damaged in Ethiopia, Kenya and Somalia, with potentially severe consequences for agriculture-based livelihoods in contexts where food security is already fragile (FAO, 2020b). Highly mobile and capable of stripping an area’s vegetation, locust swarms can cause large-scale agricultural and environmental damage. Even a relatively small locust swarm can eat the same amount of food in one day as about 35,000 people. This can be especially devastating in countries facing food security crises, where every gram of food produced counts towards alleviating hunger (FAO, 2020c).

Locusts are also serious threats to agriculture in The Caucasus and Central Asia. Three main locust pests, the Asian Migratory Locust (Locusta migratoria migratoria), the Italian Locust (Calliptamus italicus) and the Moroccan Locust (Dociostaurus maroccanus) jeopardise food security and livelihoods in both regions as well as in adjacent areas of northern Afghanistan and southern Russian Federation. Over 25 million hectares of cultivated areas are potentially at risk. During outbreaks, upsurges and plagues, these pests attack and destroy pasturelands and a wide range of cultivated crops, including cereals, cucurbits, legumes, sunflower, tobacco, vegetables, vines, fruit trees, cotton and other plants. Locusts have a direct impact on agricultural production systems, which are vital to the viability and growth of the concerned countries, which largely rely on agriculture. The most affected populations are often the most vulnerable communities living in the rural areas. Because these are mainly small landowners, following subsistence agriculture, even limited infestations can cause severe damage at this scale and threaten livelihoods, which can in turn, also lead to adverse social consequences (FAO, 2020d).

Locusts have a high capacity to multiply, form groups, migrate over relatively large distances (they can fly up to 100 km per day) and settle and breed in various habitats. These capacities enhance their prevalence at the regional level. The borders of countries in The Caucasus and Central Asia are often located across traditional locust habitats and breeding areas, and locusts frequently cross countries’ political borders. As a result, international collaboration is critical for their control. Locusts are becoming increasingly dangerous in the context of extreme weather events associated with climate change, due to their high capacity to exploit new situations. On average, over the past 15 years, locust affected area as large as almost 4 million hectares have been treated annually in Caucasus and Central Asia.

Metrics and numeric limits

Not available.

Examples of drivers, outcomes and risk management

Locusts are known as the most destructive invasive plants pests. They have the ability to change their behaviour and appearance under particular environmental conditions (unusually heavy rains) and to transform themselves from harmless individuals to a collective mass of insects that forms swarms. During quiet periods (known as recessions), solitarious locusts are found in low numbers scattered throughout the deserts of North Africa, the Middle East and Southwest Asia (Desert Locust). This arid area is around 16 million km² in size, and includes about 30 countries. It is called the recession area. In severe cases, the swarms can invade an area of land equivalent to about 20% of Earth’s surface (FAO, 2015).

Species other than Desert Locust can also cause significant damage under favourable conditions in different parts of the world. These include Italian Locust and Moroccan Locust in The Caucasus and Central Asia, Red Locust in Eastern Africa, Brown Locust in Southern Africa, Migratory Locusts in Africa and Asia, Tree Locust in Africa, and Australian Plague Locust in Australia (FAO, 2020c,d).

The main strategy for locust management, which has been promoted by the FAO for decades, relies on the so-called locust preventive control strategy. This is based on appropriate monitoring of locust habitats at key periods of their development in order to allow early detection of number increase and behaviour change, early warning, and early reaction (FAO, 2020d).

If well implemented, this approach facilitates a reduction in the occurrence and intensity of locust outbreaks and the prevention of their development into major upsurges or plagues.

Over decades, this strategy has been proved to be the most effective, making it possible to react before a significant increase in locust populations can occur. It results in: reduced damage to crops and rangelands and thus increased food security and improved livelihood of highly vulnerable rural communities; reduced negative impacts on human health and the environment (through reduced pesticide sprays); and lower financial costs. 

For such transboundary plant pests, this strategy also needs to be coupled with global or regional cooperation. The FAO recommendations for the management of the Greater Horn of Africa Region (FAO, 2020a) include:

• Informing response. Continue to assess the situation through the FAO Desert Locust Information Service and provide early warning, forecasts and advice to affected countries and international partners. 
• Control operations. Provide aerial and ground control operations support and enhance national preparedness capacity.
  • Ground control operations (hopper-stage locusts): procurement of chemical and bio-pesticides and equipment, storage, training, human and environmental safety, and disposal of chemical drums and containers. 
  • Air control operations (adult-stage locusts): contracting planes, pesticides procurement, human and environmental safety, training, and disposal of chemical drums and containers. 
• Ground surveillance and impact assessments. Facilitate ground surveillance, monitoring and continuous assessment in partnership with country governments and the Desert Locust Control Organization for Eastern Africa (DLCO-EA) with the objective of reinforcing region-wide early warning and response.