The FAO said in its latest locust bulletin on Friday, however, that some swarms had moved south, invading southern Senegal, Guinea-Bissau and perhaps northern areas of Guinea-Conakry.

The bulletin said an aircraft had been positioned in Senegal with a view to undertaking cross border spraying operations into all these countries until the end of January. Another had been stationed in Gambia, it added.

With the grain harvest is now safely in across the semi-arid Sahel belt of West Africa, the immediate threat posed by locust swarms that remain in the region is sharply reduced.

However, Guinea-Bissau is particularly exposed because the country’s cashew nut trees are currently in flower. Cashew nuts are the main export of this former Portuguese colony of 1.3 million people and provide a meager but vital source of cash for two thirds of its peasant farmers.

Locusts first appeared in eastern Guinea-Bissau on 19 December, but their arrival in the capital, which lies at the heart of the cashew nut growing area, has heightened fears that the country’s plantations of cashew nut trees may suffer heavy damage.

The economy of the small country is still in ruins following a 1998/99 civil war and three years of chaotic rule afterwards by former president Kumba Yala, who was deposed in a bloodless coup in September 2003.

International aid enabled the interim government which replaced him to pay a huge backlog of civil service salaries and finance the holding of parliamentary elections in March last year.

But the elected government of Prime Minister Carlos Gomes Junior, which emerged from those polls, is still broke.

It had to contend with a mutiny by unpaid soldiers in October and complained to donors earlier this week that it had no money to finance presidential elections, which are due to, take place in May.

Foreign Minister Soares Sambu met locally-based diplomats on Wednesday to urge them to finance this poll, which is due to complete Guinea-Bissau’s return to democracy.

The 2004 locust invasion found the countries of the Sahel and the FAO itself ill prepared to react quickly and effectively.

Large-scale control measures got under way late and locust experts fear an even bigger insect invasion when the swarms migrate south across the Sahara again in June this year unless control operations currently under way in Morocco, Algeria, Tunisia and Libya prove successful.

The Senegalese government will host an international conference in Dakar from 11-13 January to consider ways of controlling locusts in West Africa more effectively.