Plagues are periods of one or more years during which there are 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.
There have been six major Desert Locust plagues in the 1900s, one of which lasted almost 13 years. The area in which plagues occur covers about 29 million sq. km and can extend across 58 countries.
Desert Locust plagues do not occur over night; instead, it takes at least one year or more for a plague to develop through a sequence that commences with one or more outbreaks and followed by an upsurge. Nowadays, there is sufficient warning in advance that a plague is developing so countries are no longer surprise as they were in the past. This is due to regular surveys and control operations as part of the preventive control strategy adopted by FAO and countries.
Some recent plagues are described in more detail on these pages. Please see the FAO Desert Locust Guidelines (in the Publications section) for more detailed information.
1860-2017 (click to enlarge)