This is the solution for SC3KU players that are having a problem with this kind of disaster. Some say that saving and reloading the game after all the locusts has been repelled, they're swarming again and causing more chaos at the moment (especially if your cities were planned to have so many trees).
Don't panic, when you've already repelled the locusts, just wait about several minutes and the disaster should be over.
Note: I found this solution when I was about to search for it when the disaster was occurred, suddenly it's over in the meantime. Therefore, I write this solution to help you guys afterwards. 😄😎