Hi,
I work in optics and even within the industry there is a difference of opinion about fungal spores. One bench engineer refused to allow me to bring a lens into the factory when I told him it had fungus in it - lest it contaminate the environment. Other, equally well qualified colleges reckon that is total rubbish - the spores are everywhere, it is the conditions that cause the growth.
What I can say is this: I have never seen any fungal growth on any optics we work on in the UK. Not once. Never. That is because all the optics we work on are kept indoors at 'normal' room temperatures and humidity. Also, all the 'balsam' in our optics is synthetic - so no nutrients for organic life forms. Obviously I have seen fungus on camera lenses outside of my job - usually ones badly stored in a loft or garden shed or garage.
Equipment we ship to India and Pakistan often has problems.
The reason is that to get fungal growth you need the right (wrong?) conditions - that is high (ish) humidity and a bit of warmth. Dry, cold lenses do not get fungal or mould growths. Also - the fungus needs a source of nutrients. This can be the canada balsam between the elements (in which case you are in big trouble) or the (damp) layer of grime on the lens surface.
So, keep the glass clean, cool and dry and it shouldn't be a problem.
If you are in a hot humid place - well humidity is the easiest thing to control - silica gel is your best friend.
I don't think killing the fungus is likely to be so difficult if it is on the surface of the elements. Lots of things would do the trick. I've got a formula somewhere for a fungus killer which contains Hydrogen Peroxide and Ammonia. I bet dilute bleach would do the trick, too. But really, unless you are unlucky enough to live in an environment that promotes fungus growth, I don't think you need special spore killing mixtures - once it's taken out of that damp loft, cleaned thoroughly and placed in a cool, dry place in a bag with a silica gel packet in it the fungus growth will cease. Alas - if it has etched the glass then that can not be rectified.
If the fungus is in the balsam - you can't do much other than to get as much UV light through it as possible.