Who is responsible for the treatment and extermination of bed bugs - the landlord or tenant?

The laws may vary from state to state but generally speaking the landlord must pay for the extermination of bedbugs.  It is an infestation much like it would be deeded if there were mice, roaches, etc.  It all has to do with the warranty of habitability that comes with renting an apartment and your right to live in a safe, clean and healthy environment. You need to contact your landlord immediately and you also need to take whatever precautions necessary to protect your stuff.  The landlord should exterminate your whole building as a precaution as those creatures can travel quickly. If you want to double check then call your state department of housing to be sure.  Good luck.