Locust swarms were reported to be moving southward from Algeria and Libya and have recently been found in northern Niger. The FAO had earlier warned that swarms could arrive in Niger and Mali by June 2012.
Continued rains and the resulting growth of vegetation have led to the formation of swarms by mid-May 2012, said FAO experts.
"The number of locusts and how far they move will depend on two major factors. The effectiveness of current control efforts in Algeria and Libya and the amount of rainfall in the Sahel of West Africa," said FAO senior locust forecasting officer Keith Cressman.
Both Algeria and Libya have been working hard to treat infested areas, covering a total of 40,000 hectares in Algeria and 21,000 hectares in Libya at the end of May.
"In a normal year, Algeria and Libya would have been able to control most of the local swarms and prevent their movement towards the south, but insecurity along both sides of the Algerian-Libyan border is getting in the way of full access by local teams and by FAO experts who need to assess the situation. Libya's capacity to carry out control efforts has also been affected in the past year," Cressman explained.