Becky, here's an article by North Dakota university extension that has a paragraph of instructions for pasteurizing in a microwave:
https://www.ag.ndsu.edu/pubs/p...
You could test the mix for fungus gnat larvae by placing some sliced potato on it and checking under the slices in a day or so.
The label for Gnatrol should be easy to find on Google, just type in: Gnatrol msds label
I wouldn't be too concerned about perlite although I don't know for sure if it would be a problem in the microwave, since it is heated volcanic material in the first place. I would make sure it really is perlite and not polystyrene though.
