Final answer:
The Illinois Department of Public Health administers the Structural Pest Control Act in Illinois, regulating wood treatment and other pests in residential and other structures, while the EPA regulates pesticides at the federal level.
Step-by-step explanation:
The agency responsible for administering the Structural Pest Control Act, which regulates wood treatment and other pests in structures in Illinois, is the Illinois Department of Public Health (IDPH). This act is designed to safeguard public health by ensuring that individuals and businesses performing pest control services are qualified and follow state regulations. While the Environmental Protection Agency (EPA) handles pesticide regulation at the federal level through the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), it is the state-level authority, in this case, IDPH, which enforces relevant state laws concerning the commercial application of pest control practices in residential and other structures.