Which of the following pesticides banned by the EPA was used to control fire ants?

Mirex is a pesticide that was specifically used to control various pests, including fire ants. It is a chlorinated hydrocarbon that became popular for its effectiveness against fire ant populations. However, over time, it was recognized that Mirex posed significant risks to human health and the environment, leading the EPA to ban its use.

Captan, while a pesticide, is primarily used for fungal control on crops and does not target fire ants. Similarly, 2,4-D is an herbicide that is effective against broadleaf weeds but not specifically designed for pest control like fire ants. Acetamiprid is a neonicotinoid insecticide used for a variety of pests but was not notably associated with fire ant control to the extent that Mirex was.

Therefore, Mirex stands out as the correct answer because of its historical application specifically aimed at managing fire ant populations and the subsequent risks that led to its ban.