Some farmers have been upbeat during the current season, which opened on Oct. 1, about a healthy mix of rain and sun but flooding in June and July and heavy rains in the following months have spread disease, including brown rot and black pod disease, according to exporters.

Nine exporters interviewed by Reuters said cocoa arrivals at the country's ports since the start of the main crop have consistently fallen short of last year's totals, with the gap widening in October and November.

"It's becoming worrying," said one exporter. "Last season we were receiving 80,000 tonnes per month in November and now we are at 60,000 tonnes, and it seems to stagnate instead of progressing."

The exporters said they expected this season's production to stand at about 830,000 tonnes by the end of December, down from 938,000 tonnes last year.

Ivory Coast's cocoa output accounts for about 40 percent of global cocoa supply and it registered a record harvest of more than 2 million tonnes of beans during the 2016/17 season.

However, farmers' earnings were hit by falling world prices and many could not afford to apply fertilisers and pesticides in the months ahead of this year's main crop, making their pods increasingly vulnerable to disease.

"We got too much rain at the wrong moment -- just when the pods were developing, when the pods needed sunshine in September and October," said another exporter based in Ivory Coast's commercial capital Abidjan.

Exporters said last week that production could take an even bigger hit next year, falling by nearly half in the first quarter of 2018.