South American Locust outbreak

After 60 years of only small sporadic outbreaks of the South American Locust, in 2015 a large upsurge began that caused serious management issues and declarations of national emergencies. These increased populations have continued into 2020, with numerous outbreaks in the Gran Chaco region of Paraguay which spread south into Argentina as far as Santiago del Estero and over into the province of Corrientes near the borders of Brazil and Uruguay, provoking international meetings and coordination to develop response plans and upgrade regional detection systems.

What environmental conditions caused the current South American Locust outbreak?

Rainfall and elevated winter temperatures led to the expansion of suitable breeding areas and extreme population growth. In 2015, according to Medina et. al (2017), La Rioja, Catamarca, and Santiago del Estero provinces had both a mild winter and frequent rains from late winter to spring. This weather increased locust growth rate, and likely broke the winter adult reproductive diapause earlier than usual (Hunter & Cosenzo, 1990), allowing for a third generation. It also enabled the South American Locust, which usually only has two generations per year, to add a third generation of exponential population growth. The favorable environmental conditions also expanded suitable breeding areas, making it difficult for available scouting personnel.

What are the challenges to maintaining and expanding South American Locust management capacity?

Fueled by favorable environmental factors, as locusts began migrating they moved into areas with no trained personnel and little infrastructure for monitoring and management (Medina et al. 2017). The lack of long-term funding and organization led to several weaknesses in preventive strategy and is a familiar ‘vicious governance cycle’ in locust management. The GLI was invited in the early stages of the recent outbreak with stakeholders from Bolivia, Paraguay, and Argentina, to participate in round table discussions and field research trips which have since evolved into formal long-term projects to understand both the complex ecology of the South American Locust as well as the governance structures that surround it’s management in an effort to find solutions to current barriers to more sustainable and effective management.

What is the historical context of South American Locust swarms?

As explained in the September 2017 issue of Metaleptea, “The resurgence of the South American locust (Schistocerca cancellata)”

The South American locust, S. cancellata, appeared as a destructive agricultural pest in 1538, affecting cassava crops in Buenos Aires (Gastón, 1969). While S. cancellata has an expanded range during plagues—from southeast Bolivia, Paraguay, south Brazil, Uruguay, Chile, and Argentina as far as the 42°S—the biggest impact and economic losses have been in Argentina (Kölher, 1962; Lieberman, 1972). Indeed, virtually no crop in Argentina has escaped locust swarms (de Wysiecki and Lange, 2005). Similar to how the Rocky Mountain locust (Melanoplus spretus Walsh, 1866) shaped pest management in the U.S., the history of pest management in Argentina began with S. cancellata. Locust control campaigns in the early 19th century gave birth to the first governmental agency with the mission of controlling pests and regulating national plant health, a task that is now integrated into the duties of the National Plant and Animal Health and Quality Service of Argentina (SENASA). During plague years, locusts would be distributed across half the country (1.4 million km2) (Gastón, 1969). Stories were passed on at family gatherings of clear skies suddenly darkened by swarms and crops entirely lost to locusts. However, by the 1960s after many years of control campaigns heavily relying on DDT, a preventive strategy was officially established that succeeded in keeping the locust population at bay. The locusts were restricted to a relatively small region in northwest Argentina (Barrera and Turk, 1983; Waloff and Pedgley, 1986; Hunter and Cosenzo, 1990). In Argentina, 1954 was the last year a major plague period was reported (De Wysiecki and Lange, 2005). Monitoring continued in Catamarca and La Rioja provinces where locust populations remained, but was minimal elsewhere because the locust populations had diminished.

September 2017 issue of Metaleptea

Ongoing response efforts, what is being done?

The following institutions are involved directly or in a supporting role in the ongoing monitoring and control efforts of the South American Locust. See their websites for the most up to date information.

How can I help?

Research groups are also working tirelessly to make advancements in our understanding of locusts, from genomics to ecology, in an effort to more sustainably manage the natural phenomenon of locust swarming (see Research Labs section of our Resources Page). If you are working on the South American Locust and would like to be included, or have any updates or announcements please email us

Coverage of the South American Locust outbreak

Page references

Barrera, M. and Turk, S., 1983. Estado actual de la langosta Schistocera cancellata paranensis (Burm.) en la Republica Argentina: neuvos aportes a su bioecologia. Acta Zoologica Lilloana, 27, pp.15-29.

de Wysiecki, M. L. y C. Lange (2005), “La langosta Schistocerca cancellata Serville (Orthoptera: Acrididae: Cyrtacanthacridinae) en la Argentina: biología, ecología, historia y control”, en L. Barrientos Lozano y P. Almaguer Sierra (eds.), Manejo integrado de la langosta centroamericana (Schistocerca piceifrons piceifrons, Walker) y acridoideos plaga en América Lana, Instuto Tecnológico de Ciudad Victoria, Tamaulipas, México.

Gastón, J. 1969. Síntesis histórica de las invasiones de langosta en la Argentina. Publ. Misc. No. 433. Secretaria de Estado de Agricultura y Ganaderia, Buenos Aires, 32 pp.

Hunter D., Cosenzo E. 1990. The origin of plagues and recent outbreaks of the South American locust, Schistocerca cancellata (Orthoptera: Acrididae) in Argentina. Bullen of Entomological Research 80: 295-300

Köhler, P. (1962) Ecologia de la zona central y de gregarización de la langosta en la Republica Argentina. Idia Supplement No. 7, 108 pp.

Liebermann, J. 1972. The current state of the locust and grasshopper problem in Argentina. Proc. Int. Study Conf. Current and Future Problems of Acridol., London, 191-198.

Waloff, Z. and Pedgley, D.E., 1986. Comparative biogeography and biology of the South American locust, Schistocerca cancellata (Serville), and the South African desert locust, S. gregaria aviventris (Burmeister)(Orthoptera: Acrididae): a review. Bullen of entomological research, 76(1), pp.1-20.