A recent article in PCT magazine discusses Silica Dust (Cimexa), Diatomaceous Earth (DE) and related concepts.
http://www.pctonline.com/pct0814-silica-gel-research-bed-bugs.aspx
Some takeaways.
1. Silica dust (Cimexa) substantially more effective in killing bed bugs than
diatomaceous earth (DE).
2. Silica dust (Cimexa) more effective when applied dry than when sprayed in aqueous suspension. (Note: researchers only applied 1/2 label. It would have been interesting to see comparative results if applied per label.)
3. Silica dust (Cimexa) may have prophylactic role in preventing the spread
of bed bugs in multi-unit dwellings.
4. Resistance to Silica Dust is less likely than with other pesticides because of desiccant action.
5. Silica dust has low toxicity to mammals. The acute oral LD50 (lethal dose) is comparable to table salt.
6. Application can have its challenges especially by non-professionals.
7. Silica dust is often called Silica Gel. They are the same but the name can be misleading. Whichever name is used, it's a light, fluffy powder, not a gel as most people understand the term.
Richard