well.. it's not why asia has all these nasty pests.. but why human are over populating the planet and invading natural habitat of those insects. but since we are not into controlling human population, we will have to control the other end of the stick, animals, insects, plants and others. in process we more or less destroy biodiversity and some insects will become a "problem" to us human. and we forget what have we done to get rid of those "problem's' natural predators.
the areas along the south east asia have conditions that favor large biodiversity, sort of like s. american rain forests which are also going away. human hasn't exactly "harness" the environment there like we did in New York, LA, Paris, Tokyo, Seoul and other fantastic metro cities. as soon as we destroy the remaining rain forests, we won't have to worry too much about any pests... other than the ones that will survive nuclear meltdown like roaches.