Hi, this is Howard,
This sounds like an upsetting situation. From what you have reported, you respond to your son's behavior with negative consequences, i.e. punishment.
A better approach would be to reward your son when he behaves appropriately. For example, when he isn't pestering his sisters you can say "Son, I am so happy you aren't bothering your sisters. That's great!" The more you praise his these positive behaviors the more they will become part of his normal behavior.
You can also set up a reward system. At the end of the afternoon, if your son's behavior was appropriate then he gets a special treat. That can be a favorite snack, or a favorite TV program, or just a few minutes of one on one time with you. This can also be very helpful.
There are numerous books you can read for more tips. Here is a link to one that may be helpful: