How to remove application menu from XFCE Panel

Problem

I switched from Unity to XFCE by installing Xubuntu. The indicator plugin area from the Panel in Unity also appears in the XFCE Panel. Whenever I opened Firefox, I noticed that its entire menu bar would appear in the middle of this indicator area!

Solution

The easy solution is to remove the indicator plugin area from the XFCE Panel. However, I have some Unity indicators that I need to be displayed in the XFCE Panel, like the Dropbox client for example.

A better solution is to remove the Application Menu indicator itself. This is what is used by Unity to display the menu bar of an application in the Unity Panel.

I do not need this on XFCE since it shows the menu bar in the application itself. Removing this indicator is easy:

$ sudo apt remove indicator-appmenu

Restart Ubuntu to get XFCE Panel in the correct state.

Tried with: XFCE 4.12 and Ubuntu 15.04