Sinesis is very difficult to grow. It grows very slow and is difficult to cultivate. It has been show that most Sinesis on the market is Paecilomyces which isn't related to the Cordyceps Genus. Cordyceps has been out for decades in the US market under many companies. There were studies on this years ago in regards to QC issues:
1Zhu, J.S., Halpern, G.M., Jones, K. 1998. The Scientific Rediscovery of an Ancient Chinese Herbal Medicine: Cordyceps sinensis Part I. The Journal of Alternative and Complementary Medicine 4(3): 289-303.
2Chen, Y.Q., Wang, N., Qu, L.H., Li, T.H., Zhang, W.M. 2001. Determination of the anamorph of Cordyceps sinensis inferred from the analysis of the ribosomal DNA internal transcribed spacers and 5.8S rDNA. Biochemical Systematics and Ecology 29: 597-607.
3Yang, J.-L., et al. 2008. Molecular phylogenetic analysis of Paecilomyces hepiali and Cordyceps sinensis. Acta Pharmaceutica Sinica 43(4): 421-426.
4Wei, X.-L., et al. 2006. Analyses of molecular systematics on Cordyceps sinensis and its related taxa. Mycosystema 25(2): 192-202.