When they became more numerous, the authorities declared a state of emergency in November and tried to kill them -- but the swarms were simply too big.
Then Cyclone Hurana hit Madagascar in February, and the floods created a perfect breeding ground for the locusts.
"Not enough measures were taken, and so we had a locust invasion. In one day, we counted five swarms over a distance of 20 kilometers (12 miles). It's extremely serious," Andriamaroahina added.
Around 13 million people -- over half the island's population -- face food shortages or malnutrition because of the destroyed crops, according to the FAO.
Madagascar developed a 3-year emergency plan with the agency to spray pesticides by air over the millions of hectares of contaminated land.
But it is still waiting for around $40 million (30 million euros) in aid to finance the project and donors have not yet given the green light.
"The big problem here is that we don't have money, so we can't buy pesticides and we can't buy enough fuel all at once," said Rakotovao Hasibelo, a regional official of the National Anti-Locust Centre.
"The field officers, the managers can't do their work, and while we're not working, the farmers suffer and the locusts multiply," he said.
The Agriculture Ministry points the finger at mismanagement for the lack of funds.
"The National Anti-Locust Centre has a monthly budget of 2 billion ariary ($918 million, 700 million euro), but 1.5 billion ariary goes to salaries," said the ministry's Andriamaroahina.
Madagascar is no stranger to natural disasters. Droughts and cyclones regularly affect more than 70 percent of the population who live under the poverty line.