My verbena plant got infested with white flies which I realised pretty late when the leaves started looking weird.I sprayed the plant with neem oil which didn’t help and then with some stronger insecticide which killed most of the pests but a few were still alive and flying about.I have cut off the main parts of the plant hoping this will save it.

How long would it take for new growth to develop in this stage?

Please help me out with some guidance!