DDT resistance arose during a time when it was extremely intensively used to try to wipe out malaria-carrying mosquito populations. It's certainly sustained by

DDT resistance arose during a time when it was extremely intensively used to try to wipe out malaria-carrying mosquito populations. It's certainly sustained by the more moderate uses of it, but at this point, that ship has sort of sailed. It's been reintroduced in some countries as well - it's effective, and it's an important tool, but it's not nearly enough. And indoor residual spraying with DDT for malaria control remains fairly controversial - I fall in the camp of "It's probably worth it, but anything we can do to minimize it is a thing worth pursuing."