Maybe this article will help, at least for a start. However, this article is a year old and there have most likely been more precedents set since then.
Dealing with Bedbugs
by Richard Siegler and Eva Talel
New York Law Journal
November 5, 2008 Bedbugs are making a major resurgence in the United States. Through June 19, 2008, 8,840 bedbug complaints were filed with the New York City Department of Housing Preservation and Development (HPD) by rental tenants, compared with 6,889 in all of 2007, an increase estimated at 28.3 percent. HPD issued 2,757 bedbug violations in 2008, up from 2,008 in 2007, or an estimated increase of 37.3 percent.[1] Managers of co-op and condominium buildings report similar trends.[2]
After World War II, liberal use of the pesticide DDT nearly eradicated bedbugs in the United States. Their resurgence is attributed to increased international travel; restrictions on the use of DDT; and the difficulty in eradicating bedbugs. They are minuscule, hide in cracks, crevices and inside mattresses and pillows and go easily undetected. While there is a common misconception that bedbugs are attracted by unsanitary conditions, their sole objective is finding a feeding source—human blood. Although bedbug bites do not spread disease and are not fatal, they leave itchy red lesions on the skin and their nocturnal feeding habits are traumatic for victims.[3]
Bedbugs present a challenge for co-op and condominium boards: is the apartment owner or the board responsible for eradicating an infestation? This column addresses this novel issue and discusses cases in New York and other states dealing with damage to persons and property from bedbug infestations. This column also provides guidance to boards and managers in dealing with bedbug infestations in co-op and condominium buildings.
Proprietary Lease
The touchstone for board and shareholder responsibility in a co-op is the proprietary lease. Generally, tenant-shareholders are responsible for keeping the apartment interior in good repair while the co-op/lessor is responsible for keeping the building in good repair. Therefore, an apartment owner should be responsible for remediating a bedbug infestation within the apartment. However, where multiple apartments are infested and it is difficult to identify the source, the infestation may become a board responsibility. Further, even where only a single apartment is infested, the protections afforded residential tenants by the warranty of habitability may obligate the board to remediate, unless the shareholder’s personal property is demonstrably the source of infestation.
Warranty of Habitability
The warranty of habitability, codified in New York Real Property Law (RPL) §235-b, implies a nonwaiveable warranty in every residential lease that the apartment is fit for human habitation and free of dangerous conditions detrimental to the health, life, or safety of its occupants.[4]......
Click link for the rest -- it's a pdf.
http://www.stroock.com/SiteFiles/Pub663.pdf