Locust / Grasshopper

Locusta migratoria

1. Identification

• Common name: Migratory locust / Locust
• Scientific name: Locusta migratoria L.
• Order: Orthoptera
• Family: Acrididae

2. Pest description

• Adults: large insects, 40–60 mm; variable coloration (green, brown or brownish); well-developed wings; strong flight capacity.
• Nymphs: similar to adults but without developed wings; variable coloration; move in groups, causing significant damage.
• Eggs: laid in masses (egg pods) in the soil, generally in sandy or loose locations.
• Gregarious phase: under high population density, the individuals change behaviour, coloration and physiology, forming migratory swarms.

3. Main hosts

• Agricultural crops: cereals, maize, rice, sorghum, wheat, barley.
• Vegetables: lettuce, cabbages, bean, potato, tomato.
• Pastures and forages: various grasses.
• Spontaneous plants: a wide range of herbaceous plants and grasses.
• Highly polyphagous species, able to feed on more than 100 plant species.

4. Symptoms and damage

• Intense defoliation caused by the voracious feeding of nymphs and adults.
• Consumption of leaves, stems, flowers and, in some cases, fruits.
• Drastic reduction of leaf area and plant vigour.
• Severe production losses in cereals and pastures.
• In swarm situations, total destruction of crops over an extensive area.
• Indirect damage: soil erosion due to the removal of plant cover.

5. Biological cycle

• One to two generations per year, depending on the region and climatic conditions.
• Eggs laid in the soil in late spring or summer.
• Hatching after a few weeks; nymphs go through 5–6 instars before reaching the adult stage.
• Adults can live several months, with high dispersal capacity.
• Overwintering generally as an egg in the soil.
• Under favourable conditions (temperature, humidity, food abundance), population outbreaks and the formation of migratory swarms may occur.

6. Monitoring

• Direct observation of nymphs and adults in agricultural areas and pastures.
• Counting of population density by transects or grid squares.
• Inspection of laying areas to detect egg pods.
• Regional monitoring and outbreak forecasting through surveillance networks.
• Assessment of the risk of swarm formation in periods of high rainfall followed by heat.

7. Management measures

• Cultural: surface tillage of the soil to expose egg pods; management of spontaneous vegetation; maintenance of balanced pastures.
• Biological: promotion of natural enemies (e.g.: insectivorous birds, reptiles, spiders, entomopathogenic fungi such as Metarhizium anisopliae).
• Integrated protection: continuous monitoring, early intervention in nymph foci, application of measures that reduce density before swarm formation; judicious use of authorised insecticides when necessary.

Bibliographic references

• EPPO Global Database – Locusta migratoria.
• CABI Invasive Species Compendium – Locusta migratoria.
• FAO (2020). Locust Watch: Locust Biology and Ecology.
• Uvarov, B. (1977). Grasshoppers and Locusts. Centre for Overseas Pest Research.
• Latchininsky, A. (2013). Locusts and grasshoppers: biology and management. Journal of Insect Science.