Actually, as I understand it (based more on my reading about mosquitoes than about pesticides; sorry I can't give refs, but my books are packed) there is one
major problem with DDT: mosquitoes (its usual target) develop resistance to it very rapidly, usually within ten years or less. Kind of like us ebook buyers developing resistance to DRM.
The major predators of mosquitoes, on the other hand, do not seem to have the same level of biological flexibility. So when DDT is used, the mosquito population drops drastically, then rebounds, then increases because the natural predators are now missing. It works in the short term, but because of whatever quirk in mosquito biology lets them develop resistance to it so rapidly, it doesn't work as well in the long term. So it looks like a cheap and easy fix, but in the long run, you've got the flying, biting, malaria-spreading equivalent of XDR-TB on the loose, plus whatever else is going wrong with your ecosystem due to the loss of the mosquito predators which also eat other insects. As a short-term fix until other controls could be implemented, it can and does work, but not long term. Mosquitoes are adaptable little wretches.
Incidentally, at least as far as I'm aware, DDT is still legal for use for vector control in most countries; it's large-scale agricultural use that's generally prohibited, as that both causes greater environmental damage and, by exposing a larger population of mosquitoes to DDT, even those that are not near human habitation, increases the chances of resistance developing.
A combined program of pesticide-treated mosquito nets, elimination of breeding places, and yes, selective spraying when necessary, is more effective in the long run. Sure, it's not as easy as "just spray this miracle stuff around and your problem is gone" but it has the decided advantage of actually working. Since the malaria plasmodium's lifecycle involves two alternating hosts, the key to eradicating it is to break that cycle: reduce the population of infectious mosquitoes and reduce the population of vulnerable humans, so that the chances of an infectious mosquito biting a vulnerable human (or an as-yet-uninfected mosquito biting an infectious human) is virtually nil. Killing adult mosquitoes is only one part of that.
All that aside, my sig is actually referring to the word "management". When you hire a "pest management" company, you're not hiring them to teach the cockroaches to march in formation; you're hiring them to eradicate the little buggers. DDT is used to destroy insects. The whole point is you don't want
any left alive (would you hire an exterminator that advertised "we'll kill most of the bugs"?). And likewise, DRM eradicates rights, it doesn't just "manage" them.
No, it's not a perfect analogy, but I thought it was clever.
