Q.combat with lemon tree disease.
today I foynd some fungus like things in the lemon tree leaves.It is shown in the photo.Please help and suggest which remedy I will take.

This took a bit of research, but I found that your tree is infested with Asian Citrus Psyllid.
This link has more information.
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74155.html
After reading this information, it is important that you report this infestation to your local County Extension Office.
Here is a link to help you locate your closest office.