Okay, there's been a lot of hyperbole lately about the use of adverbs. Or rather the use of no adverbs. But let's get down to facts and figures (before I go out of my mind).
For a 75,000 word YA manuscript, at what number of adverbs should I start to worry (and to fiercely eliminate them)?
popmuze, there ARE no facts and figures. Truly.
If you need to be told there's a problem with 'he ran quickly' then yes, you need to check every single adverb you have to be sure it's got a purpose of its own that couldn't be replaced by the use of a strong verb.
If (like most on AW) you're a little more advanced than that, then all you need to do is check your adverbs with the same eagle-eye you check every other word you've used - is it the right word with the right rhythm meaning exactly the right thing, and if it isn't then WTF is it doing there?
That's all there is. There are no guidelines, and there are no rules. Occasionally a writer comes along like Stephen King who says 'adverbs are bad' even if he uses them himself, and the very desperate will interpret this as an absolute mantra. Those who naturally incline to the kind of purple prose that causes slushpiles to sprout broccoli will even need such advice.
Most don't. From what I've seen of your very crisp and incisive writing, I somehow doubt you do either.
Louise
PS And of course you need 'fiercely'. Personally I don't like the split infinitive, but your post isn't about my individual likes or dislikes. Your 'fiercely' is a classic example of how an adverb can convey tone (and humour) like no other word...