Speaking at a special meeting of affected countries on Tuesday, Food and Agriculture Organisation (FAO) Director-General Joseph Tchikaya said, "The FAO is taking this opportunity to launch its appeal to the international community for urgent and substantial anti-locust assistance."
Without immediate attention to the plague of locusts, the FAO warned entire fields of maize, cassava and other staple regional crops would be destroyed.
An invasion by the voracious insects has already spread to 6.5 million hectares (16 million acres) of agricultural land in the Arab Maghreb nations of North Africa and the Sahel region to the south.
One tonne of locusts - a very small portion of an average swarm - eat as much food in one day as about 10 elephants or 25 camels or 2500 people.
The government ministers from Algeria, Chad, Libya, Mali, Mauritania, Morocco, Niger, Senegal and Tunisia met to discuss efforts in their countries to deal with the problem before drafting a plan at a regional level.
"Contributions so far confirmed or promised by donors remain below our hopes and cannot at present cover needs," Tchikaya warned.
The campaign requires about $83 million, Mahmud Sulh, head of the FAO's vegetable production agency, told AFP.
Algerian Prime Minister Ahmad Ouyahia appealed to participants to "unite their voices to send the distress signal of affected countries ... to the rest of the international communutity to send immediate assistance".
Ouyahia, welcomed the ministers to the talks in Algiers, which opened a day after a meeting of experts from the countries concerned.
FAO announced on 5 July the first swarms of desert locusts were abandoning their spring breeding areas and heading into Mauritania, Mali and Senegal, with more expected in the coming weeks.
"Contributions so far confirmed or promised by donors remain below our hopes and cannot at present cover needs."
In the last two weeks, the invasion had reached Niger, Mali, Senegal and Mauritania, the FAO said in a report on Tuesday from Rome.
"The number of desert locust swarms invading cropping areas in Mauritania, Senegal and Mali from Northwest Africa has increased in the past two weeks," it said.
"In northwest Africa, where intensive control operations have been in progress since February, there are signs that the situation is improving," it reported in the one piece of good news.
"No swarms have been reported in Chad or Darfur, Sudan, but the risk there remains high. There is a potential danger that swarms could also reach Burkina Faso," FAO said.
"So far, $9 million in emergency assistance has been pledged. FAO has contributed nearly two million from its own resources and donors have provided seven million."
In mid-July, numerous swarms were seen moving south in the Adrar region of central Mauritania, causing damage to date palms, the report continued.
"Most of the swarms dispersed throughout summer breeding areas in southern Mauritania. Others continued east and south into northeastern Senegal and western Mali.
"As good rains have fallen throughout the Sahel and ecological conditions are favourable, large-scale breeding will commence shortly, causing locust numbers to increase further in west Africa."
Control campaigns in the Sahel were hampered by lack of available resources and the difficulty of locating and treating the highly mobile swarms.
Intensive ground and aerial control operations continued in northwest Africa, the agency added: "However, by mid July, there has been a decline in the number of hectares treated in Morocco and Libya.
"This suggests that the situation is starting to get better in both countries and should become calm in the region over the next few weeks."
A desert locust eats its own weight (two grams or 0.07 ounces) of food every day, according to FAO experts.
Desert locust swarms range from less than a square half-mile to hundreds of square miles in size. There are about 50 million locusts per square kilometre of a medium-density swarm.
The total number of locusts in a swarm varies from a few hundred millions to several billions.
The swarms travel a few kilometres to more than 100km (60 miles) a day, or as much as 3500km (2100 miles) in a month.