Alongside the COVID pandemic, India has to now fight the threat posed by the locust swarms that invaded vast swathes of land in India since April 11th this year. Favoured by rain-bearing winds, the desert locust swarms, after wreaking havoc in East Africa, entered several districts of Rajasthan from across the border and moved to parts of MP and some parts of Maharashtra and Uttar Pradesh within a few days causing extensive damage to the vegetation en route. It is reported that crops spread over 500000 hectares of land in Rajasthan, mostly in the western and eastern parts of the sate were damaged.

Locusts have, of course, been a bane of agriculture throughout the recoded history of man. There were locust plagues throughout the world in the 1920s, 30s, 40s, 60s, 80s, and the early 2000s. The last such locust swarm we had in India was in the early 2000s. Of course, we have been handling their periodic outbreaks with the advanced information provided by the Locust Warning Organizations (LWO) established by the erstwhile British colonial government at Jodhpur and Karachi in the Indian subcontinent in the early 1900s. After independence, LWO at Jodhpur along with other Locust watch centres in the boarder districts of Rajasthan are keeping an eye on their movement and warn farmers in advance to take appropriate measures to minimise crop damage. They also undertake spraying infected areas with pesticides using ultra low volume sprayers. Recently, they have even used ULV sprayers mounted on aircrafts and drones. However, what matters most in minimising their effect on agriculture is: detecting the swarms early and killing them as they move, but our monitoring centres are reported to be facing resource crunch for years. 

The most disturbing news about the current swarm is: experts from LWO are describing it as potentially the “worst in decades.” And the reasons are not far off to seek. The locusts that have entered India this time round are said to be of 10-12 days old and thus still have longer life-span.  Which means, they are likely to start lay eggs after the onset of monsoon and continue to breed for two more months. And each female that has a life span of 90-days can lay as many as 95-158 eggs in each pod. Further they can breed in India three times. Which means, as India is getting ready for Kharif sowings, these swarms are likely to continue for the next four months. This is likely to amplify into an agrarian disaster, for these locusts are voracious feeders and according to the Food and Agriculture Organisation, the destructive power of a typical locust swarm can be enormous.

It means, we need to move forward with better and more innovative methods to fight this menace successfully. The starting point of this fight would be to understand how this known recluse and a singleton insect that won’t mix-up with others in its group, suddenly as the crop-harvest season arrives, teams up with others and form into swarms to attack plants for food. Studying the biological mechanism that triggers this sociological transformation, Stephen Rogers of Cambridge University found that the tactile stimulation resulting out of solitary locusts touching each other while searching for food is the cause for their behavioural change. This mechanical stimulation resulting out of a touch even just in a little area of the back limbs of the insect found to affect a couple of nerves in their body leading to their coming together. Their subsequent studies shown that substantial changes in some molecules that are known to modulate their central nervous system, the most important among them being serotonin, regulates their mood and social behaviour.  In a laboratory experiment they have also found out that application of serotonin inhibitors such as 5HT or AMTP to the group of locusts reduced their coming together significantly.   

This finding raises a new hope: Can we arrest the swarms by spraying serotonin inhibitor molecules as the swarm begins to form?  This is what perhaps our experts at LWO in Jodhpur have to examine. There is also a need to study the impact of climate change on the swarm formation, for that enables us to know about the likely occurrence of swarms well in advance so that we can prepare the farming community to tackle the swarms effectively.  Meteorologists have commented that warming Indian Ocean is an indirect cause for breeding and formation of recent locust swarms. For, record-breaking rainfall in India and eastern Africa precipitated locust breeding in the moist African deserts and favourable rain-bearing winds aided their move into India. Over it, the corona related quarantine measures in Iran, Afghanistan and Pakistan that disturbed the usual coordinated efforts of these countries in controlling the swarms with insecticides had further aggravated the threat. Paradoxically, the current forecast for good rainfall in Rajasthan is sending jitters, for it would be pretty conducive for locust breeding during sowing season. And locust swarms do not respect national boundaries. So, we have to get ready with necessary wherewithal to minimise their impact on agriculture by adopting timely coordinated action along with the countries on these swarm-routes. 

While it is some comfort that there is now limited standing crop in India, forecasts for good rains in Rajasthan are feared to create conducive conditions for locust breeding during the sowing season. We need to be ready with pesticides etc., to control the second wave of swarms by killing them at the very formative phase itself. There is also a need to abandon any territorial blame game and focus on policies that will ensure an equitable, sustainable future for all.

Image courtesy Economic Times