The United Nations Office on Drugs and Crime said in a report received Friday that plant diseases in 2010 wiped out much of the opium yield, resulting in a price rise. Opium yields returned to pre-blight levels in 2011, but the price remained high, the survey said.

Definitive statistics are hard to obtain in Afghanistan.

Afghanistan provides about 90 percent of the world’s opium, the raw ingredient for heroin. The UN and Afghan government have long tried to wean the country off the lucrative crop.

Earnings from opium are also used to fuel the insurgency, financing weapons and equipment for the Taleban.