The unexpected success of the Taliban in Afghanistan in eradicating three-quarters of the world's crop of opium poppies in one season is leading experts to ask where production is likely to spring up next.

The director of the United Nations Drug Control Program, Pino Arlacchi, said there was no chance that opium from other sources would compensate this year for the loss of Afghan crops, and the prices of opium and heroin will rise substantially, with opium already worth five to seven times its usual price. His program helped convince the Taliban that opium is a disgrace to Islam.

The chairman of the Central Asia Institute at Johns Hopkins, Frederick Starr, said the West, especially Europe, had been inexplicably slow in recognizing developments in Afghanistan. ''The reduction is probably the most dramatic event in the history of illegal drug markets, not only in scale, but also in the fact that it was done domestically, without international assistance,'' he said. He added that Europe, where most Afghan heroin was consumed, had been ''stunningly dysfunctional'' in helping Afghan farmers who have sacrificed livelihoods and in moving to prevent new fields from springing up in other poor countries.

United Nations narcotics officials are looking at three regions that may be tempted -- Myanmar, Pakistan and Central Asia.