The UN food agency on Tuesday warned the unrest in northern Mali means that efforts to contain the threat of desert locusts are being hampered and appealed for $10 million (8.1 million euros) in aid.
"In northern Mali control operations cannot be carried out because of political conflict," the Food and Agriculture Organisation (FAO) said in a statement, adding that 30 trucks and other equipment had been looted.
FAO said it was expecting a big rise in locust numbers in Mali and Niger by the end of the summer because of heavy rains in the region over the past three weeks which has increased hatching by locusts last month and this month.
Keith Cressmann, FAO's senior locust forecasting officer, warned: "Swarms could move to Mauritania, Algeria, Libya and even southern Morocco as well as threaten crops during the harvest period in the Sahel of West Africa."
Locusts have now also been seen in eastern Chad and in western Sudan.
The agency said last month that desert locust swarms were moving southward from Algeria and Libya into Niger and Mali. In its statement on Tuesday it said Niger had mobilised anti-locust teams and had treated 1,200 hectares so far.
Locusts were first seen in southwest Libya and southeast Algeria in January.
FAO said France had already pledged 850,000 euros for efforts to contain the locust threat and talks were ongoing with four other donors for another $4.0 million while there had been pledges of $2.8 million in bilateral funding.
"Although Niger, Mali and other Sahelian countries have trained locust survey and control teams, funding is needed in an emergency to expand their capacity to respond on a large scale," the UN agency said.
Explore further: Locust breeding expected to rise