Q.What is this news ?
A. India should remain on high alert against locust attack for the next four weeks, the Food and Agriculture Organization (FAO) has warned amid the country facing the worst locust attack in 26 years.
• Spring-bred locust swarms, which migrated to the Indo-Pakistan border and travelled east to northern states, are expected to return back to Rajasthan with the start of the monsoon in coming days.
The current locust attack (2019-2020) has been categorised as an upsurge.
Q.What is the difference between a locust plague, upsurge and outbreak?
1. Outbreak: If good rains fall and green vegetation develop, Desert Locust can rapidly increase in number and within a month or two, start to concentrate, gregarize which, unless checked, can lead to the formation of small groups or bands of wingless hoppers and small groups or swarms winged adults. This is called an OUTBREAK and usually occurs with an area of about 5,000 sq. km (100 km by 50 km) in one part of a country.
2. Upsurge: If an outbreak or contemporaneous outbreaks are not controlled and if widespread or unusually heavy rains fall in adjacent areas, several successive seasons of breeding can occur that causes further hopper band and adult swarm formation. This is called an UPSURGE and generally affects an entire region.
3. Plague: If an upsurge is not controlled and ecological conditions remain favourable for breeding, locust populations continue to increase in number and size, and the majority of the infestations occur as bands and swarms, then a PLAGUE can develop. A major plague exists when two or more regions are affected simultaneously.
Outbreaks are common, but only a few result in upsurges. Similarly, few upsurges lead to plagues. The last major plague was in 1987-89 and the last major upsurge was in 2003-05. Upsurges and plagues do not occur overnight; instead, they take many months to develop.
There have been six major plagues in the 1900s, one of which lasted almost 13 years, the FAO website notes.
Q.What are ‘desert locusts’?
A. Desert locusts (Schistocerca gregaria), which belong to the family of grasshoppers, normally live and breed in semi-arid or desert regions. For laying eggs, they require bare ground, which is rarely found in areas with dense vegetation.
Q. How they form swarms?
A. As individuals, or in small isolated groups, locusts are not very dangerous. But when they grow into large populations their behaviour changes, they transform from ‘solitary phase’ into ‘gregarious phase’, and start forming ‘swarms’. A single swarm can contain 40 to 80 million adults in one square km, and these can travel up to 150 km a day.
Q. What are Climate link to the infestation?
A. The strong positive Indian Ocean Dipole brought torrential rainfall in 2019 for most parts of India. This extended rainfall continued in several parts of West Asia, Oman, Yemen and in the Horn of Africa – so much so that the dry sand became heavily moisture laden, facilitating the formation of several locust swarms.
Due to favourable winds, it helped swarms to fly and breed in traditional grounds in Iran, Afghanistan, Pakistan and India. The unusually mild summer this year, which saw several bouts of rainfall over north and western India from March to May, also helped the insects breed.
Q. What is FAO ?