If it was B&W, I am almost sure this has to be "The Unknown Terror" (1957).
I agree with Andrew-it even mentions the calypso singer and the song in this review from imdb-
I remember seeing this as a kid on local TV and being somewhat put out by the fact that you never got a clear look at the infected natives (probably for good reasons) and that the killer fungus monster at the finale was obviously tons of soap suds mixed in with a little dry ice fog. Oddly enough it stuck with me and soon I was putting shampoo in my hair and screaming "The fungus,the fungus!" Still,the leads all do a good straight faced job and the script doesn't contain the amount of Ed Wood style howlers you'd expect it to.As far as I know this is also the last horror film to present calypso singer Sir Lancelot who had appeared in the Val Lewton Films I walked with a Zombie and Curse Of The Cat People. The song "You Got To Suffer To Be Born Again is a mix of genius and absurdity. Highly recommended to anyone who likes old B movies.