>> I bet they used DDT to get it under control.............
No, they got it under control by releasing billions of sterilized adult males. That’s still the state of the art in screwworm control.
Are they still doing it?...........
Yes, the sterile fly program was the driving force back in the 1960s.
We raised cattle & angora goats back then. I remember helping my dad doctor infected goats & calves. We saved a few & lost a few.
I also remember coming across a couple of the cardboard boxes that held the sterile flies on our ranch.