The Geneva-based World Meteorological Organization warns the locust plague that has hit northwest Africa is likely to get worse and spread to other countries. The hot, humid weather provides a perfect breeding ground for these insects.

This is the worst plague of locusts to hit the Sahelian region in 15 years. Billions of locusts already have devastated crops in Mauritania, Senegal, Mali and Niger. The World Meteorological Organization says swarms of locusts have reached Chad and threaten to reach the war-torn region of Darfur in Western Sudan.

WMO Agricultural Meteorological Division chief Mannava Sivakumara says whole crops have been wiped out in the countries invaded by the locusts.

"Typically a locust consumes his own weight in vegetation in a day," he said. "In a swarm, you could have up to a billion locust[s] and they could literally eat 350, 400 truckloads of vegetation a day. So, not only is the farming community affected, but also even the livestock - whatever grass is left on the ground is consumed."

The World Meteorological Organization warns the wholesale destruction of much of the region's agriculture is likely to have very serious consequences for the people, 90 percent of whom are subsistence farmers.

The agency notes locust swarms are a regular occurrence in West Africa. But, this year's swarms, it says, are the worst since a 1987 to 1989 plague. It says the exceptional rains this year, which followed several years of drought, have allowed the insects to flourish.

In the coming weeks, Mr. Sivakumara says hot, humid weather will provide ideal conditions for locusts to reproduce. He says new swarms could start to form by mid-September.

"And I would say that perhaps this year, the international community was caught a little off-guard in this situation," he said. "And, all that is happening - of course, we will continue to monitor and we will monitor through the dry season and try to forecast if such a situation is likely to occur next year."

Mr. Sivakumara says the countries infested with locusts need help in acquiring the aircraft, pesticides for spraying and technical assistance to prevent these pests from devouring their crops.