By Ange Aboa ABIDJAN (Reuters) - The world's biggest cocoa supplier, Ivory Coast, closed the book on its worst harvest in at least five years on Monday, and exporters aren't expecting the new season to be any better. Loads of cocoa beans arriving at ports from the West African nation's plantations lagged last year by nearly 14 percent, reaching just 1,178,526 tonnes during the October 1 through September 30 season, according to official data. Weak production from the key world exporter, scarred by a 2002-03 civil war and racked by years of underinvestment, can bolster cocoa prices on the London and New York exchanges by restricting supply to market. Last year, cocoa arrivals at the main ports of Abidjan and San Pedro hit 1,367,877 tonnes -- the second best performance since the 2004-05 season thanks to good growing weather. But black pod disease and crumbling infrastructure have weighed heavily on Ivory Coast cocoa output. Exporters polled by Reuters last week said they projected the 2009-2010 season to run between 1 and 1.15 million tonnes. During the first four days of the new season, cocoa arrivals hit 6,500 tonnes, according to exporter estimates, well below last year's 9,692 tonnes for the same period. "The quality is good and there's no evidence of problems with the beans. We hope it continues like that. Last year there were too many problems," said the director of an export company in San Pedro.