A deadly and incurable crop disease has spread widely in Madagascar's main vanilla-producing area, farming officials said.

In a report released Monday, assessment teams said the world's main vanilla producer has to radically change farming methods to fight the fungus attacking plants at the root.

Malagasy agronomic research chief Simeon Rakotomamonjy said the situation is "critical." He said the disease has hit 80 percent of plantations around Sambava and Andapa, two of three main centers of vanilla production on the Indian Ocean island's northeast coast.

Most of Madagascar's vanilla is exported to the United States, where it is used for making confectionary, soft drinks and ice cream.