I don't see why not? You have to understand that smelling something isn't just taking in the odor that is produced by the chemical, because the odor is the molecules themselves.
It's possible to train dogs for shrooms but unlikely since shrooms aren't that mainstream to begin with. There maybe some who can, but most standard dogs probably don't. And lsd is odorless.....how would a dog sniff out an odorless chemical in micrograms?
It be nice to get a hold of one of those dogs that detect magic mushrooms right around when they come up. You could go out hunting with them and they could tell you which ones were good. That is...if they are real.
Saying something is odorless is like saying something doesn't exist. Your brain decodes the molecules that are taken in through the nostril, and the brain gives you the smell. Dogs can smell LSD if you put lysergic acid diethylamide molecules under their snout. Whether or not its enough molecules for the brain to sense it and understand what is is the big thing. I'm sure a dog can sniff out a huge blotter sheet easily (if trained of course) but for a dog to sniff out a drop in a concealed container, it's almost impossible because of the small amount of molecules there is to be picked up.
For the record I just read on a drug dog site that they train for heroin, cocaine, meth, pot, LSD and bodies. Didnt mention mushrooms, but that doesnt mean they dont train for those too. http://leerburg.com/qadrug.htm#age