I would simply find out what coercion the Taliban used to all but eradicate poppy cultivation in 2001 and suggest to the US's Afghan partners that the same methods be adopted.
The Taliban did not try to suppress opium production until they were in full control, and appear to have only done so in 2001 as part of their drive to get UN recognition as Afghanistan's legitimate government. Prior to their ban on opium production, they derived enormous revenue from taxing and sale of the crop, and continued to do so after the ban as 2000 had been a bumper crop. Some observers assert that the ban was more to restrict supply and increase profits for opium shippers, avoiding a glut on the market. In 2001, prior to September, they had authorized Afghan farmers to plant opium again (as seen in the record crops after their fall).

As for the methods? That's pretty simple. The Taliban had Pakistan on their side and had established a government that has a monopoly of force over the Afghan countryside.

So ... we should win the war first?