Unusually heavy rain last week in most of Ivory Coast's main cocoa growing regions has disturbed the development of the October-to-March main crop and disease is spreading in some plantations, farmers said on Monday.

The marketing season in Ivory Coast, the world's top cocoa producer, is underway with a new farmgate price of 825 CFA francs ($1.39) per kg set by the government early in October.

Farmers in the central and the southern regions said rainfall last week was the heaviest they had seen in the past five years, making it difficult to dry and load beans.

"It's complicated. We can't dry well and there is sure to be a lot of moisture in the deliveries in the coming days," said Roger Boka, who farms ON the outskirts of the southern region of Agboville.

Farmers said the main cocoa crop was promising as trees have a good yield, but said a continuation of heavy rains could cause young pods and cherelles to fall from trees.

Black pod disease was spreading in several plantations due to high moisture levels but crop losses should be limited, they said.

Data collected by Reuters showed rainfall in Agboville was at 87.9 millimetres (mm) last week, 63 mm above the five-year average.

Similar growing conditions were reported in the central region of Bongouanou, where rainfall was 83 mm last week, 60.9 mm above average, in the central region of Yamoussoukro, where rainfall was 61.6 mm last week, 39.5 mm above average, and in the southern region of Divo, where rainfall was 59.3 mm, 34.9 mm above average.