The problem with DDT is simple:

Insects -- mosquitoes, for example -- are R-selectors. That is, they produce enormous numbers of offspring but put very little effort into each one. Think of oysters as the ultimate R-selector, with their millions of offspring, very few of which will ever become oysters. Basically, they spew gazillions of eggs everywhere, and hope for the best. Mosquitoes are far from the champions in the egg-production race, but a female mosquito can produce about 1,000 offspring in her two-week lifespan.

The reason that matters in the case of the mosquitoes is that DDT is, as pesticides go, moderately easy for insects to develop a resistance to. Let's say there is a .00001 chance -- that is, 1 in 100,000 -- for any given mosquito to have a genome that will allow it to survive DDT application and reproduce. So out of a million mosquitoes (not, despite what I sometimes think, the content of my back yard, but easily the content of a couple of acres in a mosquito-friendly area) you'll have 10 that are resistant to DDT. With all the competing mosquitoes killed off, they will be putting out those offspring like crazy. Two weeks later, your 10 mosquitoes will be 5,000 mosquitoes, and I'm sure you can see where this is going.

The other half of this problem is that the predators of mosquitoes are more likely to be K-selectors -- that is, creatures that produce fewer offspring but make a greater investment in each one. For example, lizards will lay only a few eggs a year, but their eggs are much larger, proportionately speaking, than mosquito eggs, and their offspring are more likely to survive as individuals than their R-selector equivalents. Also, their generation times tend to be much longer. Take mosquitofish, for example. They're common around here, and I use them for mosquito control in water gardens (Gambusia can live on what they catch in water so hot it kills water lilies). We tend to think of mosquitofish as R-selectors, but of course the whole thing is a spectrum, and they're a lot further K-ward than mosquitoes are. In the time it takes a female Gambusia to produce a dozen offspring, two generations of mosquitoes can grow, lay eggs, and die. In the time it takes those dozen new fish to grow to reproductive age, those mosquitoes have gone through another four generations. So six generations of mosquitoes for one generation of mosquito predators -- 12 fish, or billions of mosquitoes.

Now, the problem comes in when you kill off 99% of the fish and 99% of the mosquitoes. Let's say you kill off all but 10 individuals of each species. Your fish can produce a brood every month (to make the math easy) and produce 12 new fish (assumed to be 6 of each sex) each time, and those fish require 2 more months to grow to reproductive age, and then a month to actually gestate their first brood, etc. So in six months, you have your original 10 fish (they live for a year or two), and their first through sixth broods. That's 70 fish, of all sizes from big adults to tiny fry. Plus their first brood of 12 (half females) has produced its first, second, and third broods, for another 216 fish, their second has produced its first and second, 144 fish, and their third has produced its first, 72 fish. So at this point, when the grandfish of the original 10 individuals are just reaching breeding age, you have a total of 1,132 mosquitofish. Meanwhile, what have our 10 mosquitoes done in 6 months? Well, that's 12 generations for a mosquito. 1,000 offspring (half female) per generation. So in two weeks, our 10 mosquitoes are 5,000 mosquitoes. In four weeks, they're 2.5 million mosquitoes ... well, you get the point. Their replacement time is much, much shorter than even a very prolific predator.

So in the end, you've got mosquitoes that are highly resistant to DDT (which was observed, by the way, within a few years of first use in any given area) and you've killed off all the other things that might eat them. Not only is your original problem back, but it's had puppies. The mosquitoes laugh at your sprays and their predators are dead.

That's the real problem. Not whether we want bald eagles or not, not whether the American Council on Science and Health is a partisan group or not, not whether any given person, group, or idea is divine or satanic ... simply, DDT doesn't solve the problem. It makes it look like it's solved for a few years, but then it's back and worse than ever ... usually after the people doing the spraying have declared the mosquito/malaria/yellow fever/whatever problem solved, accepted their awards, and moved on.

DDT has some uses. But despite what the people who want to make a political issue out of it instead of a scientific one thing, it's not miraculously better than more modern pesticides. It's not actually even all that good. It looked good when it was first introduced because it was the first really effective pesticide and it was being used on totally naive populations. Think of it, in a sense, as an analog to penicillin: amazing stuff when it first came out, but misused in numerous ways, and now virtually ineffective. Against a modern population of mosquitoes, it's about as useful as penicillin is against MRSA or multi-drug-resistant TB.

OnlyM3: Bathia_Mapes

It was legal in the U.S. until the ban in 1972. I suggest you look up "Silent Spring" and learn what DDT did to bird eggs, including those of the bald eagle. Use of DDT came close to making our national bird extinct.
I suggest you look up how that book is a complete fraud based on ZERO facts. The author is a complete fraud, right up there with Spoon benders and Dowzers.
Wrongful ban on DDT costs lives
[www.upl.co image 640x188]

But hey DDT ban kills brown people so of course you are all for it.
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From wiki:

Defenders of the book argue that Carson was sensitive to the problem of "insect-borne disease" and Silent Spring never called for the banning of DDT;[25] that when DDT stopped being used to fight malaria it was because mosquitoes had become resistant to it;[26][27] and that DDT was never banned by the US government or international treaty for use against malaria (its ban for agricultural use in the United States in 1972 did not apply outside the US or to anti-malaria spraying, the international treaty that did ban most uses of DDT and other organochlorine pesticides - the 2001 Stockholm Convention on Persistent Organic Pollutants - included an exemption for DDT for the use of malaria control until affordable substitutes could be found.[27])

Any rebuttal?

What a great talking point. We should absolutely lift the ban on any chemical that has some positive use. I wonder if there is some other substance we've outlawed that has shown some ability to do something positive... to alleviate suffering if you will.....

I'd be willing to bet the same people who are wanting to lift the ban on DDT because it's a cheap pesticide it helps with bedbugs are also completely against legalization of marijuana, despite its known medical benefits to cancer patients. It's almost as if they aren't being logically consistent with their arguments.

DDT is actually no longer effective against bed bugs. This was reported by the L.A. Times about 2-3 months ago. Turns out that a lot of bugs that DDT was used against are now resistant to it.

Sorry.

The American love-affair with carpet in shiatty appartments and hotels is a large factor to blame. Carpet wastes a lot of resoures, is difficult to clean. Concrete with paint on it is a better choice.

But hey, carpet is a consumable and feeds the economy.

cman: Bathia_Mapes: It was legal in the U.S. until the ban in 1972. I suggest you look up "Silent Spring" and learn what DDT did to bird eggs, including those of the bald eagle. Use of DDT came close to making our national bird extinct.

Of course, it had an unintended consequence: bird strikes on airplanes are on the rise because of the rebound of birds

/The moar you know

Less birds are dying from bird strikes than would be if DDT was still legal, since most of the higher level birds would be very close to extinct or actually extinct at this point.

Worldwalker:
So in the end, you've got mosquitoes that are highly resistant to DDT (which was observed, by the way, within a few years of first use in any given area) and you've killed off all the other things that might eat them. Not only is your original problem back, but it's had puppies. The mosquitoes laugh at your sprays and their predators are dead.

This, THIS, THIS!! This can not be repeated enough, given all the righties under the dangerous and ignorant delusion that nature exists to serve mankind. If you push nature, nature pushes back, usually with nasty, unintended consequences.

/regret that I can click the "smart" button but once for this
//and for brantgoose

Hmmm.... My cat is now toxic to fleas. After we tried less drastic measures, Advantage was the thing that finally knocked down the flea infestation. I like the avermectin idea. I haven't had a bedbug problem (knocking on wood) but if I do, becoming toxic to bedbugs would be sweet revenge.

PaLarkin: Bathia_Mapes: It was legal in the U.S. until the ban in 1972. I suggest you look up "Silent Spring" and learn what DDT did to bird eggs, including those of the bald eagle. Use of DDT came close to making our national bird extinct.

When Rachael Carson did her studies mentioned in the book, she fed the birds a diet low in calcium.

Did she feed every fish-eating bird on the Continent low calcium? Do you have an explanation for why the shells of ALL fish-eating birds became fragile, then magically became slowly better after the DDT ban?

If you want to eradicate mosquitoes, you can't go wrong with good old Bacillus thurigensis, or BT:

\Kymry: DDT needs to be approved for certain situations.

From your link: DDT remains legal for insecticide use in most areas where malaria is a major killer

Kymry: DDT needs to be approved for certain situations.

No it doesn't. There are plenty of fine chemical products available which do not cause permanent harm. To suggest DDT is "special" is to suggest that Chemists found the bestest pesticide first, which is extraordinarily unlikely.

Seriously. How much denial to you need to be in to close your eyes to the fact that nest failure in the DDT was observably due to egg shell thinning, and that this problem went away with DDT? Or that the bird species whose populations declined were precisely those you would predict to decline if a pesticide was the source of problems? Or that the population declines were most severe in the bird species you would anticipate would have the most exposure to a persistent pesticide?

All the fish eaters died off, except those which locate food far out to sea. What is your magic explanation for that?

OnlyM3: I suggest you look up how that book is a complete fraud based on ZERO facts. The author is a complete fraud, right up there with Spoon benders and Dowzers.

Bullcrap. It's obvious to even casual observers that birds were wiped out, and are coming back well finally.

Also, there are plenty of fine pesticides available to use which don't last forever in the ecosystem. Use any one of them to get the same useful effect as DDT.

As mentioned previously, the insecticides we use now are similar in mechanism to DDT, just not nearly as dangerous to everything else. Bringing back DDT won't work, and will just bring back the harmful side effects. Once an insect becomes resistant to a certain mechanism of action, you can't go full herpaderp and expect a product using the same mechanism to work better, just because it did in the past. Failmitter and those who agree need to do a little bit of research before claiming they know better than actual experts.

/Sodium ion channels, how do they work?
//I wonder if there is correlation between people who think bringing back DDT would work and people who don't understand/believe in evolution.

I cannot believe that there are people here who are actually advocating the return of DDT. It is a horrible toxin and a powerful carcinogen. All I can guess is that those advocating weren't alive before the ban.

frank249: I recall a truck going through neighbourhoods spraying a fog of DDT to control mosquitoes with kids running behind it.

Yes, I remember this. And I know now that the kids who did this have much higher rates of cancer and having children with birth defects.

There are much better and eco-friendly ways of controlling mosquitos than pesticides. I used to work on a campus on the coast that had a lot of fresh water sloughs in the woods. The mosquito problem there was very bad. Arial spraying of pesticide didn't work. Then the county's mosquito abatement program enlisted the help of a invertebrate zoologist at the local university. His solution: place Gambusia holbrooki, the eastern mosquitofish, in the sloughs. It worked like a charm.

DDT was a harmful pesticide when they used it indiscriminently via aerial spraying. I recall a truck going through neighbourhoods spraying a fog of DDT to control mosquitoes with kids running behind it. They should not have banned it completly. It is very efective in controling mosquitoes when applied indoors on walls. Malaria cases increased in South America after countries in that continent stopped using DDT. Research data shows a significantly strong negative relationship between DDT residual house sprayings and malaria rates. In a research from 1993 to 1995, Ecuador increased its use of DDT and resulted in a 61% reduction in malaria rates, while each of the other countries that gradually decreased its DDT use had large increase in malaria rates. South Africa is one country that continues to use DDT under WHO guidelines. In 1996, the country switched to alternative insecticides and malaria incidence increased dramatically. Returning to DDT and introducing new drugs brought malaria back under control.

A mosquito was heard to complain
That a chemist had poisoned his brain
The cause of his sorrow
Was paradichloro
Diphenyltrichloroethane.

/Relevant and the nerdiest limerick I know.

Bathia_Mapes: It was legal in the U.S. until the ban in 1972. I suggest you look up "Silent Spring" and learn what DDT did to bird eggs, including those of the bald eagle. Use of DDT came close to making our national bird extinct.

In 1962 Rachel Carson's lyrical yet scientifically flawed book Silent Spring was released. The book argued eloquently but erroneously that pesticides, and especially DDT, were poisoning both wildlife and the environment and also endangering human health.

Read this article: Link

Well, we don't have malaria here anymore because of DDT.

I hate mosquitos and if means a few birds might go extinct, so be it