Cocoa crops in the world's top producer, Ivory Coast, are being ravaged by caterpillars but authorities are playing down the new scourge, saying they have it under control.

The west African nation, now a beacon of stability and prosperity in the restive region, is slowly emerging from about a decade of low-level civil war and political turbulence, and is desperately trying to restore its once-booming economy to its former glory.

"This is the new menace for cocoa cultivation," a researcher at the Ivory Coast National Centre for Agronomy said.

Authorities say some 17,000 hectares (42,000 acres) of cocoa have been ravaged in a few weeks but stress that it is a fraction of the country's total cocoa fields.

"This caterpillar attack will not have a significant impact on production as about 20,000 hectares have been affected out of the total crop area of two million hectares," said Nanga Coulibaly, who works for the national cocoa board.

Kra Kouame, the local head of agriculture at Taabo in southeastern Ivory Coast, said cocoa crops in the village of Lelebele had been wiped out in a month.

- 'Like a nightmare' -

Maxime Brou, a 48-year-old cocoa farmer from a small village in the Taabo region, said his life turned topsy-turvy in the space of just four days.

"One Monday, I went to my fields and everything was normal. Four days later, there was nothing. It was like a nightmare!" he said.

The cocoa industry, which accounts for 15 percent of GDP and more than 50 percent of export receipts as well as two thirds of the country's jobs, is absolutely vital to Ivory Coast's economic welfare, according to the World Bank.

"Caterpillars are not new for us but this is the first time they've attacked cocoa crops," said Nanan Kouame Kan Kouame, the chief of Ahondo -- a village of 5,000 people.

Cocoa board adviser Coulibaly said global warming had reduced the caterpillars' natural predators -- which includes birds and beetles -- leading to a leap in their population.

"But the situation is totally under control" and pesticide teams have been deployed across the country, he said.

The caterpillars have also attacked banana plantations, which are already reeling under a drought.

Between 2014 and 2016, rainfall in the region fell drastically from 1,100 millimetres (43 inches) annually to 900 mm in 2015. In the first six months of this year there were only 13 days of rain against 28 days in the same period in 2015.

"In June, there were only four days of rain and then nothing", said village chief Kouame.

Francois Kouakou Konan, a 41-year-old farmer said he watched on helplessly as the caterpillars "ate up" his eight-hectare field in a week.

"How will I send my young brothers and my children to school?" he asked, teary-eyed.