The UN Food and Agriculture Organisation (FAO) warned on Friday that a new generation of locust swarms was taking to the skies in Mauritania and others would rise into the air across West Africa over the coming weeks.
"A massive amount of fledging has started in southeastern Mauritania and new swarms are beginning to form," the FAO said in its latest update on the insect plague which threatens to destroy food crops across the Sahel just before they are ready to harvest.
The Rome-based organisation said locust breeding was also in progress in northern and central Senegal, northern Mali, northern Burkina Faso, western Niger and probably in Chad too.
"Consequently a substantial number of swarms are expected to form in September," the FAO said, warning that "significant crop damage" had already taken place in several countries.
Agricultural experts are particularly concerned about the situation in Mauritania, where most of the locust breeding has taken place so far, but where control efforts are regarded as grossly inadequate.
Hilde Niggemann, the head of emergency operations at FAO, told a meeting of humanitarian agencies in Dakar on Wednesday that about two million hectares of land were infested with locusts across West Africa, of which 1.6 million were in Mauritania.
Each female locust lays up to 90 eggs at a time. These take 10 days to hatch into black flightless lavrae known as hoppers.
The hoppers rapidly congregate into dense black hopper bands of up to 10,000 insects per square metre that look like liquid tarmac.
After three weeks, these hoppers grow wings and take to the air to form new swarms of locusts that often cover several square km.
Each insect weighs about two grammes but can eat its own weight of vegetation in a day and can lay three or more sets of eggs during its lifetime if weather conditions are favourable.
The FAO has estimated the cost of locust control operations at US$100 million. Some $37 million have already been committed by donors and the FAO said this week it had $16 million available to spend immediately on priority purchases of insecticide, spraying equipment, vehicles and radios and the charter of crop spraying planes.
The organisation stressed on Friday that control operations in all countries were hampered by insufficient resources, adding that "International assistance is deperately required to supplement major efforts already underway and to prevent the situation from deteriorating further."
It said there had been one unconfirmed report of a locust swarm being sighted in Sudan's troubled Darfur province, but the situation there was likely to be "less serious" than in West Africa.
The FAO said an invasion of locusts reported in northwestern Nigeria last month had been caused by Tree Locusts, not Desert Locusts, the species which is threatening to cause most damage across the Sahel.
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