Mold, like so many public health problems that are hidden and festering, finds a way to jolt us with distressing reminders of how nasty and costly it can be.

The sight of it coating the interior surfaces of Kennedy Theatre had that effect this week, a realization that was all the more disheartening because the spores undoubtedly had lingered invisibly there, and elsewhere on the frequently damp campus, for a long time.

University of Hawai'i officials made a sensible decision to close the theater long enough for a thorough cleaning as a way to manage the risk without sidelining more than one main stage production or losing class facilities for longer than a few months. The implication is clear that, even without the inundation of last November's flash flood, many buildings on campus need inspection and cleaning before a similar mold "bloom" forces critical action.

It's not just in rainy Manoa, of course, that people should be concerned. As city officials discovered during budgeting in June, mold remediation can add to the red ink on the ledger if such expenses aren't anticipated. The council was right to fatten the allotment for Honolulu Hale complex repairs by $8 million because of mold and asbestos, another pervasive problem in older buildings.

Whether buildings are privately or publicly maintained, mold is a threat that's better handled earlier than later, when it becomes costlier in every way.