How to get rid of white flies on Hibiscus Plant

Recently, I had white flies on my Hibiscus Plant. They were growing in numbers and had caused some damages to the leaves of the Hibiscus Plant. There was black dust on the leaves and I thought that it was due to the pollution in the air or some renovation works from my neighbours. However, after checking the internet for information on the white flies, I realised that the white flies will excrete honeydew after they fed on the plant sap.

I was going to buy some pesticides in the local floral shop until I saw the formula in the internet. I was sceptical at first and thought that it might not work. In my workplace, there is IPA which is Isopropyl Alcohol available.

The formula for one litre spray is:
(1) 2 parts IPA
(2) 5 parts water
(3) 15ml of liquid detergent

I don't have one litre spray, I only have a 300ml spray. I just make sure that the ratio of the IPA:Water is 1:2.5 and then the liquid detergent, I just estimated.

After putting all the ingredients into the spray can, I shook it a little to make sure that they were dissolved and sprayed onto the leaves. I sprayed the underneath of the leaves to cover the eggs and larvae. Some of the liquids did drip into the soil and I hope it would not damage the plant. I sprayed it in the morning before the sunlight became too strong. I left the plant alone for the whole day.

The next morning, I checked the plant and discovered that the white flies were gone. The eggs and larvae had dried up and were destroyed by the spray. I noticed that some leaves turned yellow and I assumed that it was due to the liquid. I will keep on monitoring the plant to see any stress that it might have.