I do not quarantine at all, unless the hoya appears sick or has obvious pests. If pests, I dip the affected plant in my alcohol/baby shampoo/water concoction, and wait for it to completely dry, before moving it to a sunny area, away from any other plants. I then treat with systemic pesticide (unless it is a cutting...no roots to absorb the systemic-in this case, I do a quick dunk in the systemic). If the infestation is bad (never happened yet), I repeat the alcohol/baby shampoo treatment once a week, until there are no more bugs, or until the systemic kicks in and nukes them all.

I have yet to obtain a diseased or virused plant. Here is what I would do, if I did:

For fungus or bacterial issues, I'd just cut the affected areas, treat with a fungicide (for fungus, I normally use my copper spray for roses) or bactericide (triathlon or phyton, depending on what I have on hand). They get quarantined until they are no longer showing symptoms +3 days.

For virused plants, it's bye-bye. I take pics, burn 'em and message the seller.

My rule has always been to buy from vendors that are either required to use systemics (overseas only) or buy from reputable vendors (both overseas and National). I also very rarely purchase without actual images of the actual plant (or mother plant, in the case of cuttings).

Thanks. This may be a stupid question, but how can you always tell the difference between bacterial and viral?

It's easier to tell the difference between bacterial and viral vs. bacterial and fungal. I actually send samples off, if I am unsure. But most bacterial and fungal infestations present with some type of squishy rot (at least, in hoyas) and viruses are NOT common (in hoyas) and usually present with asymmetrical streaking in the leaves and flowers, or bullseye patterns on the leaves (again, in hoyas). On variegated plants, the variegatioms will not have clear borders, the variegations will appear streaked. You can see this best in hosta leaves affected with hosta virus x:

Normal variegated hosta leaf (image courtesy of landscaping.about.com)-note the clear borders of variegation:

Variegated hosta infected with hosta virus X (image courtesy of plantsgalore.com)-note the "smeared", and irregular borders of variegation:

another hosta leaf infected with hosta virus x (courtesy of plantsgalore.com):

Here are images of hoyas infected with viruses:

Hoya calycina infected with capsicum chlorosis virus (courtesy of Scot Nelson-flikr):

Hoya imperialis 'Mosaic', a hoya imperialis "cultivar" (using that term loosely for this example...virused cultivars should be destroyed, not distributed, just because the flowers are neat) thought to be infected with a mosaic virus. Flowers (image on pintrest):

It is important to note that if this particular imperialis, does, in fact, carry a virus, it does not seem to affect the plant negatively. That being said, who knows how it could affect other plants? Better safe than sorry!

Great information! Do distorted leaves present a possible virus?

No...they're just typical obovata leaves. Obovata and kerri can throw some ugly foliage.

Whew, that's good news. Thanks so much.