I was going to guess that they used something like industrial-scale mosquito dunks. You put them in water and they release a live bacteria (bacillus thuringien

I was going to guess that they used something like industrial-scale mosquito dunks. You put them in water and they release a live bacteria (bacillus thuringiensis subspecies israeliensis) that specifically attacks mosquito larvae and is harmless to everything else as far as we know. https://summitchemical.com/products/mosquito-dunks/ https://summitchemical.com/products/mosquito-dunks/ Mosquito fish are also effective, and the article says they use those. Dragonflies are another very efficient predator of mosquitoes. I could imagine Disney World maintaining dragonfly ponds around their properties. Though I guess if you're good enough at controlling mosquito larvae then the dragonflies might migrate elsewhere where they have more to eat. (It'd be an interesting strategy for Disney to grow species of mosquitoes that don't attack humans and releasing them around their park, just to attract more mosquito-eating predators.)