Mauritania needs up to $20 million, 15 airplanes and 640,000 litres of pesticide to contain a locust plague engulfing its arid plains, the West African nation's top locust fighter said on Thursday. Swarms spread across almost all of the country, roughly twice the area of France, on Thursday after invading the capital Nouakchott, eating everything green in their path including the city's main soccer pitch and the president's gardens. "These swarms are a serious threat to the nation's crops, plants and even livestock," Mohamed Abdallahi Ould Babah, head of the agriculture ministry's anti-locust centre, told Reuters. He said Mauritania's army had just one operational airplane, and that the environment ministry had 10 teams on the ground to fight locusts but needed nearer 60. West Africa is facing its most serious locust crisis for 15 years, with swarms moving rapidly across Algeria and Mauritania to countries such as Mali, Senegal, Niger and Gambia, many of whose inhabitants are subsistence farmers. --MORE 2336 Local Time 2036 GMT