Short answer: mold or pests from a building defect or normal conditions are usually the landlord's to fix, under the implied warranty of habitability. If the tenant caused it, an unreported leak, blocked ventilation, infested furniture moved in, the cost can shift. Only a few states have a law written specifically for mold or bed bugs; most run on general habitability instead.
Mold: who pays
The deciding factor is cause. Mold tied to a leak, plumbing failure, or ventilation problem the landlord controls is the landlord's to fix under ordinary habitability. Mold substantially caused by the tenant's own failure to keep the unit clean and ventilated can relieve the landlord of that duty.
Virginia has the clearest mold-specific statute found: disclose visible mold at move-in, remediate within 5 business days, and an ongoing duty to prevent moisture buildup and promptly fix any mold that develops:
"Maintain the premises in such a condition as to prevent the accumulation of moisture and the growth of mold ... Where there is visible evidence of mold, the landlord shall promptly remediate the mold conditions."
Code of Virginia §55.1-1220
California's mold-specific law is narrower, just a state-approved health-risk disclosure booklet (not yet triggered as of this research). Repair liability runs through general habitability, and the landlord owes no duty to fix mold "substantially" caused by the tenant's own failure to keep the unit clean and ventilated (Civil Code §1941.2).
Texas has no mold statute. Its general repair law (Property Code ch. 92) requires fixing a condition that "materially affects the physical health or safety of an ordinary tenant" after written notice, but carves out tenant-caused conditions:
"Unless the condition was caused by normal wear and tear, the landlord does not have a duty during the lease term ... to repair or remedy a condition caused by: (1) the tenant; (2) a lawful occupant ... (3) a member of the tenant's family; or (4) a guest."
Texas Property Code §92.052
Arizona, Indiana, and Maryland have no mold-specific law either, each relies on a general fit-and-habitable duty, mold argued as a health hazard under it. New Jersey also has no mold statute (confirmed against the EPA's 50-state bed bug survey, which lists no New Jersey entry); there, landlord responsibility comes from the judge-made implied warranty of habitability, the landlord covenants that "there are no latent defects in facilities vital to the use of the premises for residential purposes" (Marini v. Ireland, as restated in Berzito v. Gambino).
Bed bugs and pests: who pays
Same deciding factor: who caused it, and who was told about it. A few states spell out the cost allocation directly.
New Hampshire has the most explicit rule found here, landlord pays by default, but can shift the cost if the tenant caused it:
"The landlord shall bear the reasonable costs of remediation of an infestation of bed bugs, but may recover those costs if the tenant is responsible for the infestation ... the landlord may bill the tenant, in writing, for the reasonable costs of remediation of the infestation of bed bugs in the tenant's own unit."
N.H. Rev. Stat. Ann. §540:13-e
Maine puts both the timeline and cost on the landlord: inspect within 5 days of a tenant's notice, contact licensed pest control within 10 days if infested, and take reasonable measures to treat it. California bars leasing a unit with a known infestation and requires written notice of findings within 2 business days, but creates no duty to inspect absent notice:
"This section does not impose a duty on a landlord to inspect ... if the landlord has no notice of a suspected or actual bed bug infestation."
California Civil Code §1954.602
Arizona bars leasing a known-infested unit but creates no damages claim against the landlord, so cost allocation defaults to the general fit-premises duty. New York City goes further than any statewide law: its Housing Maintenance Code makes extermination mandatory and landlord-funded, and requires disclosing a unit's bed bug history for the prior year.
New York State overall has no bed bug statute, it falls back to the implied warranty of habitability (Real Property Law §235-b), which excuses the landlord where the condition "has been caused by the misconduct of the tenant." New Jersey has no bed bug statute either (confirmed by its absence from the EPA's 2023 fifty-state survey, which lists a specific law for 21 other states but not New Jersey); liability runs through the same Berzito/Marini doctrine, applied in a case where the premises were "infested with roaches and rodents" among many other defects recited in the opinion.
The bottom line
- Building defect, leak, or normal conditions: usually the landlord's.
- Tenant-caused, an unreported leak, poor ventilation, infested items moved in: cost can shift to you.
- Few states have a dedicated statute (Virginia for mold; CA, ME, AZ, and NYC for bed bugs). Everywhere else, including New Jersey, runs on general habitability law.
Look up your state's rule on the state directory, browse by issue, or ask directly.
This is general information, not legal advice; confirm your state/city rule.