Qwt installation QT_PLUGIN_PATH

Qwt installation QT_PLUGIN_PATH

I have the following problem. I'm trying to use qwt qith Qt Creator, I
read the documentation downloaded the files, qmake, make, make install
worked fine and created everything under /usr/local/qwt-6.1.0. My Qt
folder is ~/Qt5.1.0
So I'm trying to change the QT_PLUGIN_PATH within the qt.conf file.
[Paths]
Libraries=../lib/qtcreator
Plugins=/usr/local/qwt-6.1.0/plugins:/plugins
Imports=imports
Qml2Imports=qml
But if I do the Qt Creator won't start, when I change it back to just
Plugins=plugins it works fine.
I also tryed the bashrc entry but no luck ether. Thanks for help.