Heavy downpours in Nigeria's key cocoa growing belts in the last two months have slowed the start of the 2010/11 main crop with only small volumes of beans trickling into the market, farmers and dealers said on Friday.

The main crop in the world's fourth-biggest grower usually starts either in late September or early October, but this year the harvest is yet to begin in earnest due to the rains.

"The main crop has not yet started fully," Afun Adegbulu, president of the Cocoa Association of Nigeria (CAN) told Reuters by telephone from Akure, the capital of southwest Ondo state, which accounts for around 40 percent of the country's output.

"The rains were almost too much in August and September, and it is still raining in October. Many farmers are worried because they don't know when the rains will stop."

The pattern of rainfall in Nigeria was in line with the trend in the West African cocoa region, which produces about two-thirds of the world's cocoa, industry experts said.

Heavy rainfall does not only raise the threat of disease on plantations, but also makes it difficult for farmers to ferment and dry beans to meet minimum export standards, dealers said.

The heavy showers are also unfavourable for maturing cocoa pods, which could affect crop output, industry experts said.

Some farmers and dealers said they expected the rains to subside in the next two weeks, with isolated showers until mid-November to provide enough soil moisture to extend the main crop's peak period to March from January.

"The late start of main crop is an indication that the peak season will go beyond January and last up to even March when the crop should be ending," Felix Oladunjoye, secretary of the Cocoa Processors Association of Nigeria (COPAN) told Reuters.

Meanwhile, in Cameroon, the world's fifth-largest cocoa producer, exported about 19,198 tonnes of

cocoa beans during the first 10 weeks of the 2010/11 season, according to statistics from the Port of Douala on Friday.

The quantity shipped included 4,120 tonnes that were exported during the week ended Oct. 9 at an average price of 1,390 CFA francs ($2.99) per kg. Cocoa exports from the central African country totalled 197,000 tonnes in the August-July 2009/10 season, a decline of almost 4 percent from the previous year which the government has blamed in part on smuggling.