The time-tested method of repelling locusts from crops in East Africa is to bang on a metal bucket and whistle loudly. When swarms afflict five countries and swell to the size of Moscow, more drastic measures are needed.

In Kenya, police facing the country’s largest outbreak in 70 years have fired machine guns and tear gas into swarms in an effort to prevent them from consuming fields. Ethiopia is spraying pesticide from small planes to displace hovering throngs, though swarms have forced passenger jets in the region to make emergency landings.