DDT as an insecticide wasn't discovered until 1939. And the question isn't whether DDT is effective. It's is it more effective than what they are using now?
Simple answer.....yes. It is more effective because it is persistent (doesn't degrade in the environment as fast). Why was it banned....because it is persistent. But there are places where you actually want persistence...like termite-proofing your house. The total ban should be repealed, and limited usage allowed.
DDT was invented in the 1860’s. It was use for insecticide much earlier than 1940.
As to what is being used now we are being blasted with neurotoxins and genetically enhanced mosquitoes. What could be worse?