In 2019 and 2020 desert locust swarms moved out of the Horn of Africa through Iran and Pakistan into India, the worst incursion in about twenty-five years.
Punjab's south-western districts, Fazilka and Muktsar, on the Rajasthan and Pakistan edge, were the entry point. Swarms crossed the border and were fought with spraying, drums and whatever noise villages could make.
The damage in Punjab was limited compared with Rajasthan and Gujarat, and it was limited because the swarms arrived when the fields were largely bare.
The Locust Warning Organisation, which maintains a network of monitoring stations in the desert belt including in Punjab, is a colonial-era institution that had almost nothing to do for two decades and then had everything to do in one season.
Locust control depends on cooperation across the Iran, Pakistan and India border, and that cooperation happened, quietly, in 2020, at a moment when nothing else between the two countries was working.
Climate projections suggest more frequent swarm-favourable conditions, which means the border cooperation that worked once will be needed again.
The desert locust breeds in the Arabian and African deserts and moves east through Pakistan into Rajasthan and the Punjab border districts when the conditions favour it.
The 2019 and 2020 swarms were the largest in decades and reached Fazilka and beyond. Control is by aerial and ground spraying and by warning, and the warning system is international.
The historical outbreaks were far worse. The famines the settlement reports record in the nineteenth century frequently followed a locust year on top of a failed monsoon.