Kabul, Afghanistan (CNN) -- Opium production has dropped significantly in Afghanistan, in large part because of a plant infection in the country's war-torn south, a U.N. report said on Thursday.
"This is good news but there is no room for false optimism; the market may again become lucrative for poppy-crop growers so we have to monitor the situation closely," said Yury Fedotov, executive director of the U.N. Office on Drugs and Crime.
The development was detailed in the office's 2010 Afghan Opium Survey. Insurgents in Afghanistan have financed their operations through the opium trade.
The report said the total 2010 production was estimated at 3,600 metric tons, down 48 percent from 2009.
"The decrease was largely due to a plant infection hitting the major poppy-crop growing provinces of Helmand and Kandahar particularly hard," the report said.
"Plant diseases are a normal occurrence all over the world. In Afghanistan, which produces 92 per cent of the world's opium, they can affect the poppy crop. The current strain attacks the roots of the plant, climbing up the stem and causing the opium capsule to wither away. These signs are similar to those observed in previous such outbreaks in the region," the report said.
Prices of opium are rising after a decline from 2005, the report said.
"In the short run, the decline in opium production has pushed prices up. Despite the drop in overall production, the farm-gate income of opium farmers rose markedly. Now that opium is commanding high prices again, the gross income for farmers per hectare has increased by 36 per cent to $4,900.
The report said opium cultivation remained stable with 98 percent of cultivation taking place in nine provinces in the south and west of the country.