Locust Tree

Description:

This Guohuaishu (国槐树) is to be found in the surroundings of Beijing University. The leaves have now changed into a beautiful yellowish color after carrying beautiful green leaves and with flowers throughout the summer. I have a question concerning the white 'paint' on the trunk. Does anyone know what it is? For bugs or fungus?

Notes:

http://en.wikipedia.org/wiki/Styphnolobi...