Neem oil doesn't get rid of fungus. It's meant to treat against bugs, which can spread fungal infections. The mode of action is double, but this lead to the myth that neem oil acts as an antifungal material.
What's the problem here? The off white gooey looking stuff or the white freckles which seem to be primordial roots emerging from the trunk.
The gooey stuff looks like some kind of biofilm or bark. I don't expect it to be fungal because fungi are rarely transparent and rarely living out in the open like that. Could be some epidermal/bark layer that's shedding. Is it actually gooey, is it dry? Does it fall apart in flakes, or does it act like a shell of some sort?
I've seen a fair share of parafilm accidents, could it be that someone left a patch of that stuff on the trunk?