You need to do a bit more reading on DDT and its effectiveness against return of bedbugs. I don't have the time right now to lay it all out for you, but if you really believe in science to back up your claims and not mere assertions, then I challenge you to do that reading from reputable sources. But in short, there is plenty of evidence that bedbugs began developing resistance to DDT well before the ban.
Here's a few reference to help you get started.
http://www.bioone.org/doi/abs/10.3954/1523-5475-25.1.41
Susceptibility of the Bed Bug Cimex lectularius L. (Heteroptera: Cimicidae) Collected in Poultry Production Facilities to Selected Insecticides
C. Dayton Steelman, Allen L. Szalanski, Rebecca Trout, Jackie A. McKern, Cesar Solorzano, and James W. Austin
Journal of Agricultural and Urban Entomology 2008 25 (1), 41-51
Yoon, K. S., Kwon, D. H., Strycharz, J. P., Hollingsworth, C. S., Lee, S. H., and Clark, J. M. (2008). Biochemical and molecular analysis of deltamethrin resistance in the common bed bug (Hemiptera: Cimicidae). Journal of Medical Entomology. 45: 1092-1101. (LRS accesstion #185379)
Zhu, F., Wigginton, J., Romero, A., Moore, A., Ferguson, K., Palli, R. … Palli, S. R. (2010). Widespread distribution of knockdown resistance mutations in the bed bug, Cimex lectularius (Hemiptera: Cimicidae), populations in the United States. Archives of Insect Biochemistry and Physiology. 73: 245-257. (LRS accesstion #188346)
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