KABUL, Afghanistan, Sept. 2 — Afghanistan’s opium harvest this year has reached the highest levels ever recorded, showing an increase of almost 50 percent from last year, the executive director of the United Nations Office on Drugs and Crime, Antonio Maria Costa, said Saturday in Kabul. He said the increase in cultivation was significantly fueled by the resurgence of Taliban rebels in the south, the country’s prime opium growing region. As the insurgents have stepped up attacks, they have also encouraged and profited from the drug trade, promising protection to growers if they expanded their opium operations. “This year’s harvest...