This country town is a secretive centre for big pharma drug production and an alleged cartel

Major pharmaceutical drug crops are a strange sight amongst the family farms and peanut crops of Queensland's South Burnett region.

The winding rows of native Duboisia shrubs snake through red volcanic soils on a massive scale.

Global pharmaceutical companies have quietly built a lucrative supply chain from the town of Kingaroy for decades.

"For a long time there were a lot of secrets kept about Duboisia, for whatever reason I don't know, because I saw there was no value in keeping things quiet," former grower Russell Exelby said.

Duboisia leaves contain the drug hyoscine, which is highly sought after for use in over-the-counter motion sickness and stomach pain medications.

A local Duboisia grower, speaking to the ABC on the condition of anonymity because of financial risk, said not even farmers knew much about the opaque supply chain of the drug companies.

"Once it leaves the farm gate, you don't have any idea of what's going on, so yeah, [it is a] very secretive industry and very controlling," the farmer said.