Can a praying mantis ootheca die of humidity?

Some time ago, I found a New Zealand praying mantis laying an egg and the next day I collected the egg and hung it from a branch. I sprayed the container I put it in with water every day and now I’m worried that it has got too much humidity and might die of because of fungus, because I found a thin layer of white substance on it, so I am very worried. Please tell me, what to do?