The locusts swarming across West Africa have reached parts of northern Nigeria, devastating fields of crops.
A locust swarm can devour as much food as 1,000 people
"The destruction done by the locusts is enormous, as a lot of farmland has been eaten up," said Zamfara state spokesman Ibrahim Birnin-Magaji.
The swarms reached Nigeria as the UN made an urgent appeal for $100m to help contain them.
The Food and Agricultural Organisation (FAO) has also said that the situation could worsen, with new swarms forming.
The locusts are also wreaking havoc in neighbouring Sokoto state.
"For the past six days locusts have been ravaging farmland in the Isa, Sabon Birni, Goronyo and Wurno local government [areas]. A lot of farms have been destroyed," said state spokesman Mustapha Shehu.
He said that the state had leased aircraft to spray pesticides, but this would not be effective unless neighbouring states co-operated, reports AFP news agency.
Mauritania remains the worst affected country, with officials saying that up to 80% of the harvest has been eaten and one million people could need food aid.
After visiting there on Wednesday, FAO director Jacques Diouf regretted that earlier warnings from his agency had gone unheeded.
"Our first request [in early July] was for $9m, but as the funds did not arrive, the scale of the problem now calls for 100 million dollars," he said.
He said this could be the worst locust invasion since 1987-9, when "$600m and five years of struggle was necessary."
Locusts have also landed in vast numbers in Chad, Mali, Niger and Senegal.
There are also fears that they could spread into Sudan's troubled Darfur region, where tens of thousands are at risk from war, disease and hunger.
The FAO's Clive Elliott 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.
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.
The eventual extent of the damage depends largely on the weather.
The more it rains, the more the locusts will breed as they travel.