I believe that a 20% bleach solution does kill OE spores, that's what most labs recommend using to disinfect rearing containers, enclosures, anyplace a diseased monarch has been. And it's recommended to soak milkweed leaves in a 10% bleach solution for 20 minutes before using as caterpillar food. Last December 2012, I saw a photo on a site comparing the appearance of an OE spore (magnified of course) when treated with 2 different bleach solution strengths, but I can't find that page now. The bleach kills the spore, and stops cross contamination.
I soaked a dead butterfly in strong bleach for 5-10 minutes, to see what dead spores look like, so I'd be able to know when I have successfully killed them on my milkweed leaves and eggs, but I don't think they were all dead. Some were lighter than others, and the OE clumps still looked dark. I guess I have to find a different way to compare spores. The microscope I ordered on Amazon, claiming to be able to magnify from 60X-150X for $40, didn't magnify more than 10X, so you get what you pay for.
Blazing star, do you soak your milkweed in a bleach solution before using, and do you test your monarchs before releasing them?
Are you a Monarch Way-Station? I'd like to find out more about what that entails. Once all these pupaes are eclosed, I will be free to resume my life. All my slides from today's group were OE positive, and they were beauties. Very discouraging.