Berthold rays are a form of deadly radiation that can cause living animal tissue to disintegrate. There was no known cure or antidote except for the mind-controlling Omicron spores.
The planet Omicron Ceti III was bombarded in Berthold rays, but unfortunately the rays were not known to Federation science until 2267, after a few colonies had already been established on the planet and wiped out under unknown circumstances. The last colony, the Omicron colony of 2264, was protected by spores. The colony had to be relocated because living animal matter could only survive on Omicron Ceti III for a week without protection. (TOS: "This Side of Paradise")
Calamarain probes were known to produce non-lethal broadband emissions, including Berthold rays. (TNG: "Deja Q")
The Star Fleet Medical Reference credits an Earth scientist, Ernst Berthold, for having artificially produced the radiation subsequent to its discovery.