Why is there a desert locust problem this year and why are they enteri...
Jun 22, 2020
Why is there a desert locust problem this year and why are they entering the cities and the urban areas? Discuss.
Desert locusts normally live and breed in semi-arid/desert regions.
For laying eggs, they require bare ground, which is rarely found in areas with dense vegetation. So, they are more likely to breed in Rajasthan than in the Indo-Gangetic plains or Godavari and Cauvery delta.
Locusts aren’t dangerous as long as they are individual hoppers/moths or small isolated groups of insects, in what is called the “solitary phase”.
It is when their population grows to large numbers – the resultant crowding induces behavioral changes and transformation from the “solitary” to “gregarious” phase – that they start forming swarms.
A single swarm contains up to 40-80 million adults in one square km and these can travel up to 150 km in one day.
The above large-scale breeding and swarm formation, however, takes place only when conditions turn very favourable in their natural habitat, i.e. desert and semi-arid regions.
The main locust breeding areas in the Horn of Africa, Yemen, Oman, Southern Iran and Pakistan’s Baluchistan and Khyber Pakhtunkhwa provinces recorded widespread rains in March-April. East Africa.
And these swarms have come not only to western Rajasthan, but also moved to the eastern parts of the state and even Madhya Pradesh and Maharashtra.
Much of this movement, it seems, was aided by the strong westerly winds from Cyclone Amphan in the Bay of Bengal.
Thus, there are two meteorological drivers behind the current locust invasions: one, unseasonal heavy rains in the main spring-breeding tracts in March-April, and, two, strong westerly winds.
After July, there would be westward movements of the swarms, as they will return to Rajasthan on the back of the changing winds associated with the southwest monsoon.
These are locusts that voraciously feed on vegetation, but have not yet laid eggs.
Once they start breeding, the swarm movement will cease or slow. Also, the breeding will happen mainly in Rajasthan.
So far, the swarms haven’t caused much damage, since the rabi crop has already been harvested and farmers are yet to start kharif sowings.
These insects need to munch enough – roughly their own weight in fresh food every day – before being ready for mating. With no crops in fields now, they have ended up invading green spaces, including parks, in cities and orange orchards near Nagpur.