do not disturbate

You can see why Johnny Foreigner has so much trouble. Even English words that appear to derive from similar roots have subordinate forms derived in different ways. For instance, we say disturb and perturb, but we say disturbance and perturbation. Come to that (if you'll pardon the pun) we say masturbation, but we say masturbate instead of masturb (just as we don't say disturbate, though some do say perturbate, wrongly I would say).

I was thinking (as you do) earlier about words ending in the fairly unusual combination -esce. Words that spring to mind are coalesce, luminesce and fluoresce, and that's about it off the top of my head. It appears the latter two, at least, are verb back-formations from the original adjectives luminescent and fluorescent, which brings other words like adolescent and pubescent into the equation, and begs the question why (this single reference aside) the equivalent back-formations haven't caught on....

Dad: Where's Nigel?
Mum: In his room.
Dad: What's he up to?
Mum: Well, he said he was going to adolesce for a while, and then pubesce later on if he had time before Top Of The Pops.
Dad: So, wanking, then.
Mum: Yes.

Postscript: a couple of others spring to mind: convalescent and putrescent. Just to illustrate the point, the first of those does have a fairly commonly used verb form, while the second doesn't - i.e. we say convalesce, but we don't say putresce. The very similar word putrefaction provides the verb form putrefy which does the same job, so maybe that's why.