Chip says:

We do not use bleach. It is too corrosive and, if not controlled, it dissolves the corrions of the eggs. Also it is not as effective as chlorine dioxide in killing all forms of microbes. We use Oxine.Oxine/Purogene/Keeper

Stabilized Chlorine Dioxide Industry-Leading Manufacturer

It is cheaper than bleach and up to 20 times more effective. We use 100 ppm for eggs and 500 ppm for all surfaces in the lab.

I have never seen any evidence that O. e. spores are within eggs or adult tissues. All the spores are on the outside of the newly emerged adults to the best of my knowledge.

On Nosema: I have an undergrad working on this problem. We sent him to Illinois to get some training with Leellen Solter. Nosema can be detected in meconium but low infestations are easily missed. So, we are moving on to egg tests. In India, all batches of silkmoth eggs are screened for Nosema. We will see if we can do something similar with monarchs. If we can, it shouldn’t be too hard to initiate and maintain Nosema free stocks.

Dr. Orley Taylor of Monarch Watch