Uganda scrambled to respond to the arrival of the biggest locust outbreak that parts of East Africa have seen in decades, while the United Nations warned Monday that "we simply cannot afford another major shock" to an already vulnerable region.

As locusts by the billions — yes, billions — descend on parts of Kenya in the worst outbreak in 70 years, small planes are flying low over affected areas to spray pesticides in what experts call the only effective control.

The hum of millions of locusts on the move is broken by the screams of farmers and the clanging of pots and pans. But their noise-making does little to stop the voracious insects from feasting on their crops in this rural community.