Desert locust (Schistocerca gregaria): biology, outbreaks and impacts

Characteristics and behaviour

Desert locusts exhibit phase polyphenism: individuals adopt either a solitary or a gregarious form depending on population density and environmental cues. In the gregarious phase they change in colour, physiology and behaviour, becoming more mobile and tolerant of crowding. Winged adults are strong fliers and can be carried long distances by winds, enabling a swarm to cross national borders and even seas. A single swarm can consume very large amounts of vegetation in a short time, stripping crops, pastures and native plants.

Life cycle and reproduction

Breeding is tied to rainfall and the availability of moist sandy or loamy soil for egg‑laying. Females deposit egg pods in the ground; nymphs (also called hoppers) emerge and, when crowded, move in cohesive bands until wings develop and adults take flight. Under favourable conditions there are typically two to five generations per year, and rapid population growth can follow sequences of rain and vegetation growth. These biological traits make early detection and rapid response important for outbreak prevention.

History, notable outbreaks and impacts

Plagues of desert locusts have been recorded for centuries and periodically cause severe agricultural damage. Large upsurges in recent decades have led to significant crop losses and local food shortages; for example, a major upsurge in 2004–05 affected parts of West Africa. More recently, extensive breeding and invasions have challenged governments and humanitarian agencies in the Horn of Africa and neighbouring regions. While locusts alone do not usually cause widespread famines, they are an important contributing factor to food insecurity when combined with drought, conflict and market disruptions.

Management and control

Responses to locust outbreaks combine surveillance, early warning and rapid control operations. Typical measures include:

• Monitoring by ground teams, remote sensing and community reporting to detect breeding sites early.
• Targeted control using ground or aerial application of approved insecticides to destroy hoppers and adults before they form large swarms.
• Increasing use of biological agents and reduced‑impact pesticides in sensitive environments.
• Regional coordination and information sharing to track movements and plan joint operations.

Notable facts and distinctions

The desert locust differs from many other grasshoppers because of its pronounced ability to change behaviour and form vast, highly mobile swarms. This capacity makes it potentially the most dangerous of the locust pests for agriculture in its range. International bodies and national agencies maintain monitoring systems and contingency plans to reduce the risk of large outbreaks and to limit the socio‑economic harm when they do occur. For general background on locust biology and management see resources on locust species and regional reports available through agricultural authorities and international agencies.