The wacky Post-it note war between rival ad agencies in Tribeca is about to end — thanks to humorless building managers.

Workers who have been decorating their windows with Post-its at Havas Media at 200 Hudson St. were told to cease and desist.

“Unfortunately, our building management team has asked that all parties (including our neighbors across the street) take everything down before we all head out for the Memorial Day weekend,” an email from a worker said.

No reason was given.

Havas employees and workers at other firms at nearby 75 Varick St. have been competing with their whimsical displays and messages.