没有意义的行为meaningless behaviour(Britain); meaningless behavior(US)

乱来to mess about

无理取闹to act unreasonably

• 种地不上肥料才是瞎闹呢。

  Planting crops without fertilizer is just senseless.

• 事情重大，可瞎闹不得。

  Things are serious. You mustn't act senselessly.

• 你规矩些，别瞎闹。

  Be a bit more well behaved. Don't be silly.