Is my plan to stop drug trade viable?the us and all industrialised nations buy the opium and coca crops?

Question

they use whats of value and destroy the remainder before criminals can obtain them

Answer 1

No, this would stimulate the trade in drugs and those farmers who currently are not raising them would switch to those crops, as a price is assured.  This has, in fact, been tried in Afghanistan.

Answer 2

As long as there is a buyer, there will be someone ready to sell at a black market price. Some nations make their most money from the sale of illicit drugs, that money runs their economy.

Answer 3

Yeah, thats a great idea. The real question is "How much would it cost to buy all the fields?" Then your next problem is "How much compensation for future revenue?"

Then your next problem is "Whats to keep someone else from growing and selling it?"

Face it the only way to stop the black market for drugs is to legalize it and tax and control it.