Katitika, Kenya – The worst outbreak of desert locusts in Kenya in 70 years has seen hundreds of millions of the bugs swarm into the East African nation from Somalia and Ethiopia. Those two countries have not had an infestation like this in a quarter-century, destroying farmland and threatening an already vulnerable region with devastating hunger.

"Even cows are wondering what is happening," said Ndunda Makanga, who spent hours Friday trying to chase the locusts from his farm. "Corn, sorghum, cowpeas, they have eaten everything."

Even a small swarm of the insects can consume enough food for 35,000 people in a single day, said Jens Laerke of the U.N. humanitarian office in Geneva.

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About 70,000 hectares – 172,973 acres – of land in Kenya are already infested. A single swarm can contain up to 150 million locusts per square kilometer of farmland – an area the size of almost 250 football fields, authorities say.

"We must act immediately," said David Phiri of the U.N. Food and Agricultural Organization, as donors huddled in Kenya's capital, Nairobi, a three-hour drive away.

Locusts swarm acros a highway at Lerata village, near Archers Post in Samburu county, approximately 300 kilomters (186 miles) north of kenyan capital, Nairobi on January 22, 2020. TONY KARUMBA/AFP via Getty Images

About $70 million is needed to step up aerial pesticide spraying, the only effective way to combat them, the U.N. says. That won't be easy, especially in Somalia, where parts of the country are in the grip of the al-Qaida-linked al-Shabab extremist group.

The rose-colored locusts turn whole trees pink, clinging to branches like quivering ornaments before taking off in hungry, rustling clouds.

Astonished by the finger-length insects, children dash here and there, waving blankets or plucking at branches to shake the locusts free. One woman, Kanini Ndunda, batted at them with a shovel.

Farmers are afraid to let their cattle out for grazing, and their crops of millet, sorghum and maize are vulnerable, but there is little they can do.

One especially large swarm in northeastern Kenya measured 60 kilometers long by 40 kilometers wide (37 miles long by 25 miles wide).

"The locals are really scared because they can consume everything," said Francis Kitoo, deputy director of agriculture in southeastern Kenya's Kitui county. "I've never seen such a big number."

The locusts eat the fodder for animals, a crucial source of livelihood for families who now worry how they will pay for expenses like school fees, he said.

His own concern about the locusts?

"They will lay eggs and start another generation," he said.

A changing climate has contributed to "exceptional" breeding conditions, said Nairobi-based climate scientist Abubakr Salih Babiker.