YAMOUSSOUKRO, Ivory Coast (AP) _ An invasion of grasshoppers and locusts threatens to spread to new areas of central and southern Africa, despite efforts to control the pests, a U.N. agriculture official said Wednesday.

Lukas Brader, director of emergency locust operations for the United Nations Food and Agriculture Organization, said 75 to 80 million acres of Botswana in southern Africa are infested by locusts.

Insect swarms threaten to spread to Angola, South-West Africa, Zimbabwe, Mozambique and Swaziland. ''That situation is very serious,'' he said. ''We may not be able to get that under control for a year or two.''

In East Africa, locusts are breeding in the coastal area of Ethiopia and may move into Sudan, he said.

Spraying operations have begun in Sudan and Ethiopia, as well as in Botswana. But Brader said it was too early to tell the extent of the infestation in those areas.

''East Africa could become more dangerous than the west,'' Brader said.

Rains in Africa have produced favorable breeding conditions for grasshoppers and locusts, whose numbers had been kept in check in recent years by severe drought. Grasshoppers have invaded West Africa, particularly Mali, Burkina Faso, Mauritania and Niger.

Pesticides and aircraft are available in affected areas, but the logistics of where and when to spray the breeding grounds are still being worked out, Brader said.

The FAO says grasshoppers threaten to devastate 2.5 million acres of arable land in the Sahel, as the semi-arid region of West Africa is called.

In normal times, Brader said, the pests damage 5 to 10 percent of the African harvest. But the FAO estimates the damage has climbed to 30 to 40 percent in affected areas.

The FAO expert complained that the African governments ''reacted very slowly to our warning cry'' and were responsible for the gravity of the situation. It is Africa's worst infestation of locusts and grasshoppers in 40 years, according to FAO reports.

The FAO monitored the spread of the locusts and grasshoppers early this year and urged governments to send out teams to do further monitoring, Brader said.

Most countries did nothing, he said. Niger, one exception, got the situation under control at an early stage with aerial spraying and other methods, Brader said.

The FAO reports that about $20 million in aid has been pledged for the anti-grasshopper campaign. Donors include a number of European nations, Canada, China, the United States and the OPEC Fund.

Swarms containing billions of insects can consume 80,000 tons of millet, sorghum and corn in a single day. Grasshoppers and locusts, when carried by the wind, can travel up to 56 miles a day.