How do you disable a secondary display on a Mac?

I have a plasma TV attached to my Mac Pro. I use it maybe once a week, to watch movies. Rest of the time it just stays connected to my Mac. The problem is that Spaces in bird eye’s view always displays a box for the plasma, which makes my main display’s box too small.

Is there a way to disable the secondary display without actually unplugging it?

Sorry this happens to be a year later, but I was just looking for a way to disable my secondary display and came across SwitchResX. It has a taskbar menu item to quickly disable any connected monitors.

I'm not sure if this will solve your Spaces issue, but it might be worth a try.

Since SwitchResX is not free, I have developed a simple free alternative, that allows you to turn off a specific Monitor.

https://github.com/Eun/DisableMonitor/releases

The only thing I can come up with which worked for me was to turn on mirroring (in the monitor menu in your menu bar, or in the screen preferences pane) and then turn off the secondary display. Spaces will then only show one display.

When you want it back (for watching movies, etc.), turn on the display and turn off mirroring.

This solution feels very kludgy to me, so I'm hoping there's a better answer (like 3rd-party software or a hidden pref which can be set via Terminal). But it should suffice for the short term.

I found a different approach which works for my use case - showing a single monitor when connecting remotely to a multi monitor setup using Screen sharing.

All you have to do is enable "Display Mirroring", and the mac will automatically make it so all apps that were on different monitors are now on the one monitor.

More info in this similar question on AskDifferent stack exchange