Chad has appealed for international aid after locust swarms, which hatched in north-west Africa, reached the country.
Chad needs planes as well as pesticides to fight the swarms
Foreign Minister Nagoum Yamassoum said Chad lacked the pesticides and equipment to fight the infestation.
He said resources had already been stretched by nearly 200,000 refugees from western Sudan and the population now faced the threat of famine.
Swarms are reported just 400km from the Sudan border, where within days they could add to the current Darfur crisis.
Another swarm is reported near Lake Chad.
On Tuesday, the United Nations warned of a serious shortfall of funds to combat the swarms, saying less than half the $50m needed had been made available.
They could be the worst swarms in 15 years, the Food and Agriculture Organisation says.
The Algerian authorities have been flying in thousands of tonnes of pesticide to its southern neighbours, and have also deployed 16 teams of specialists equipped with spray guns and navigation instruments.
They are set to be joined by other teams from North Africa but none have yet been sent to Chad.
The BBC's reporter in Algiers says that the North African states are concerned that if the current invasion of locusts in the Sahel is not tackled, the insects could go back north.
But the FAO's Clive Elliott Once says the locusts are likely to stop once they reach Sudan until the end of the summer and then start to breed again.
If the vegetation dries up due to a lack of rain, he says, they will then move in search of food across the Red Sea to Saudi Arabia.
This is unlikely to happen before October.
Locusts have already landed in vast numbers in Mauritania, Mali, Niger and Senegal.
Major foods such as cassava and millet are being damaged, as are cash crops vital for export earnings.
Locusts can eat their own weight in food every day, which means a single swarm can consume as much food as several thousand people.
In Mauritania, officials speak of 80% of the harvest gone and a million people at risk of famine.
The eventual extent of the damage depends largely on the weather.
The more it rains, the more the locusts will breed as they travel.