All natural, or 'green' doesn't mean it's any safer than a chemical.
There is naturally occuring arsenic, and olenander is a highly toxic plant just by itself. Just because something is all natural doesn't mean it's harmless or won't kill a animal. Many pesticides are 'all natural' and harmless to the environment, yet still toxic to animals. Also, remember that many things that your skin would be fine with can harm your snake(pain killers in neosporin being a classic example). Cancer is all organic and natural.
Mites and ticks are very tough bugs. Things that kill them are bound to be toxic, or they wouldn't kill the bug. I applaud the idea, but doubt you'll find much useful.