Plague of locusts casts shadow over Africa

Torn by war, famine and disease, the world's most tortured continent faces a new horror: the biggest swarms of locusts for 15 years. Steve Connor reports on a gathering menace

A plague of biblical proportions threatens the fragile agricultural communities of west and central Africa: the culprit is a six-legged munching machine called Schistocerca gregaria, the desert locust.

A plague of biblical proportions threatens the fragile agricultural communities of west and central Africa: the culprit is a six-legged munching machine called Schistocerca gregaria, the desert locust.

The Food and Agriculture Organisation (FAO) in Rome has warned repeatedly that not enough is being done to contain the immense swarms of locusts eating their way through vast swaths of food crops stretching from Mauritania in the west to Chad in the east.

Dense clouds up to 25 miles long and containing billions of insects have been sighted in southern Mauritania, northern Senegal, Mali and Niger. The FAO said there was a high risk of them spreading to Burkina Faso and the troubled Darfur region of western Sudan. Further south, Gambia has declared an national emergency.

One swarm struck the Mauritanian desert capital, Nouakchott, stripping first outlying crops then the what there was of urban greenery, including the grass from the football pitch. the people lit fires and rattled tin boxes half-filled with stones but that had little effect on the hungry insects.

The FAO said the situation was getting worse by the day, because prolonged rains after years of drought have helped the locusts breed quickly and go through four generations in quick succession.

"This is the worst occurrence of locusts in 15 years," Keith Cressman, a locust forecasting officer at the UN agency, said. "We don't have a plague now, but we're heading down that road.".

The Maghreb region of north Africa - Morocco, Tunisia, Algeria and Libya - was the first to be seriously affected this year. "Now the rains have stopped there, and conditions are becoming dry in north-west Africa," Mr Cressman said.

"Any locusts that escaped control operations there are moving over to west Africa. In the next couple of weeks, the situation will probably return pretty much to normal in north-west Africa but it will get worse in west Africa."

Subsistence farmers are worried that crops sown in this rainy season could be destroyed as fast as they germinate, creating havoc with an already fragile food supply. Jidhoum M'Bareck, who lives near the Mauritanian town of Kaiedi, works a field with a horse and plough on which between six and 10 people depend. "I can't just stand here with my arms crossed," he said. "I have to plant my crops even if I know the locusts are going to come and eat them."

A locust can devour its own body weight in food each day and some swarms are composed of billions of them. One ton of locusts - a small proportion of a single swarm - can eat the equivalent of 10 elephants, or 25 camels or 2,500 people.

During quiet periods, known as "recessions", the desert locust in Africa usually confines itself to its breeding grounds in the arid and semi-arid regions of Algeria, Libya, Morocco and Tunisia. But during plague years, aided by heavy rains, they move rapidly south into the richer agricultural regions.

Worldwide, the desert locust can during a plague year populate 11 million square miles of land, affect some 60 countries and have the potential to affect the livelihood of 10 per cent of the world's population. This year, Mauritania suffered the brunt of the initial onslaught from an advancing army of juvenile locusts, called "hoppers", which can travel between three and 80 miles a day.

In Senegal, the FAO has had reports of swarms, and hopper bands were along the Senegal river valley and in the Ferlo valley of Linguere. Sengalese officials have treated 16,000 hectares of land infested land between 8 July and 13 August.

In Mauritania, locusts swarms were reported in the capital Nouakchott. The first fully mature adult locusts of the summer generation could appear there by the end of the month, the FAO said.

Mohamed El Haceu Ould Jaavar, head of intervention at Mauritania's National Locust Centre, said this was only the beginning of the breeding season yet the position was already far worse than the last locust plague of 1988.

"It is critical," he said. "We don't have the means to cope. We need vehicles, planes and pesticides to treat the locusts. We have prepared an action plan for international donors, partners and the FAO, which envisages mobilising 50 to 60 field teams and treating up to 800,000 hectares. We can tap into army reservists for personnel. They are already trained, but we need equipment and cash pesticide. If the international community doesn't intervene it is going to be a disaster for our country."

Clive Elliott, head of the FAO's locust group, said the locust plague was outstripping all attempts at controlling its spread. "The problem is that the international donor community is being pressed on all sides to help with different problems globally," Dr Elliott said.

"It takes a while for the penny to drop in terms of realising the situation really is serious. Unfortunately, the locusts get on with their reproduction and each generation they go through makes the problem worse."

The FAO estimates the cost of treating the locust outbreak will be between $58m (£32bn) and $83m. But so far only $14m has been committed by donor countries, the FAO said.

There is nothing new to the idea of a locust plague. The desert locust is depicted in the bas-reliefs carved into the ancient tombs at Saggara in Egypt and it was the insect described in the Book of Exodus as the cause of the eighth plague that dogged the Pharoah.

One of the unusual features of the desert locust is that it can exist in two seemingly different forms. One is solitary and almost harmless and the other is gregarious, with a voracious appetite for any greenery that it encounters.

In fact, so different were these two forms of Schistocerca gregaria that scientists did not even think them to be the same species until the 1920s. Precisely why and how the solitary form can transmute into the gregarious form is still a matter of some dispute among many entomologists.

The answer appears to lie in the lifecycle of the insect. Female adults lay up to 200 eggs at a time in holes they dig out of wet ground. Thousands of locust eggs can be buried in a square-metre patch of land.

After hatching, the young "hopper" locust passes through five or six stages of growth before it finally emerges as a fully mature adult with wings. It is during the growing hopper stages that the locust eats most voraciously. One of the neat tricks the locusts can perform is to alter the speed at which they develop to suit the availability of food or wet weather. When conditions are poor, they slow their metabolism. When conditions get better, the life cycle speeds and they mature faster.

When hoppers find themselves living in densely populated conditions, they undergo a change in behaviour and colour to become the gregarious, swarming form of the species. Solitary hoppers, born green can under these conditions turn into the mature, yellow form and go on to swarm.

There is no evidence that locust plagues occur with any regularity. There were five occasions in the 20th century when deserts locusts swarmed but for no obvious reason other than because the wet weather and food supply were favourable.

The present plague is almost certainly going to get worse before it gets better. More breeding will take place this month and even larger swarms could begin to appear by mid-September to threaten the autumn harvest. At present, the only effective method of locust control is by spraying with organophosphate chemicals applied in what the FAO describes as "small, concentrated doses" from sprayers mounted either on vehicles or light aircraft.

For farmers living in the affected areas, the environmental price of using such pesticides seems a small one to pay. As 82-year-old Amadou Binta Thiam, in the affected region of Mauritania, said: "I have a big family. Twenty people depend on me. We have no children working outside who can send me money. If locusts get my field, it is a real catastrophe."

Similar sentiments wer expressed by Ahmed Ould Bah, a local herdsman who relies on good pasture land. "When the locusts spend the night here, they don't leave anything. I have to go farther and farther away to find grazing."

Locusts may seem an ancient plague from a distant time, but they are still capable of causing a very modern misery.