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639 Views 4 Replies Last post: Mar 28, 2013 9:31 PM by Remo RSS
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Feb 23, 2013 9:15 PM

How does pesticide work?

If any one knows that would be great x thanks! Also I will research it and if I find out I'll post it x

  • Currently Being Moderated
    Feb 28, 2013 10:20 AM (in response to animal lover)
    Re: How does pesticide work?

    Hi,  That's a difficult question to answer as there are many different types of pesticide and they work in different ways, and there are many different types of pest too (viral, bacterial, animal, fungal, etc.). Do you have a specific one or type in mind?

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    Mar 26, 2013 10:26 PM (in response to animal lover)
    Re: How does pesticide work?

    Interesting question!

     

    Here are some examples I found of resistance:

     

    1.  Vitamin K is essential for the blood clotting mechanism.  Warfarin (rat poison) works by interfering with an enzyme that is essential for using vitamin K

     

    Warfarin-resistant rats have a mutation that produces a slightly different form of this enzyme.   This variant enzyme is not affected by warfarin, so these “super rats” survive the poison.

     

    2. Organophosphate insecticides affect vital enzymes, called esterases to kill the insects.  Resistant mosquitoes were found to have either a duplication of the gene to produce these enzymes or damage to the mechanism that “switches off” enzyme production, so that too much is made.  As the insecticide blocks production of esterase the mosquitoes that could produce more than needed survived.

     

    3. Some antibiotics make use of  bacteria’s ability to actively absorb the substance that kills them.  For example, the antibiotic may be similar to the bacteria’s food, or other essential substance, and clogs the absorbing mechanism for that substance  (The same kind of thing happens with carbon monoxide poisoning in humans: CO binds more tightly to haemoglobin in our blood than oxygen does, so there is less room for the oxygen that we need.)

     

    Antibiotic resistance therefore may be due to a fault (such as a mutation) in the uptake mechanism.  If the bacteria are unable to take up much poison they will most likely survive, while their non-resistant companions are killed.

     

     

    But such resistance always comes at a cost.  The altered enzyme in warfarin resistant rats is less efficient than the normal form and they need about 10 x the usual required dose of vitamin K.  Mosquitoes that produce too much enzyme suffer if the excess isn’t affected by insecticide.  Antibiotic-resistant forms of bacteria, such as MRSA, are less able to compete with non resistant ones in absence of antibiotics.  In the example given, the faulty food-absorbing mechanism (which gives resistance) is also less efficient so they cannot reproduce as fast.

     

    [So although these are examples of natural (or in this case non-natural) selection, it is a mistake to call it “evolution” as many do, because there is no aquiring of totally new kinds of genetic information, only damage, or at best duplication of existing information.]

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    Mar 28, 2013 9:31 PM (in response to animal lover)
    Re: How does pesticide work?

    Theres loads of really clever stuff.

     

    Theres a type of mouse poison (alpha chlorolose) that causes hypothermia (death by cold). Great when a building is cold not so good in a centrally heated house. It can't be used outside as its an acute poison and is far to lethal to get into other animals by secondary poisoning. Its usefully as a poison as its highly effective on small animals, like mice, whereas its less effective on bigger animals like us. Other acute poisons tend to be as effective on us as them.

     

    Or diatomaceous earth which is a white powder made from siliceous sedimentary rock. Its non poisonous but lethal to insects that crawl over it. The tiny particles get in between the insects exoskeleton and scratch its surface. The insect dies by drying out (an insects worst enemy). Useful as its none toxic and can be sprinkled directly on carpets to control things like fleas.

     

    Others are effective by their formulation. Theres oil based insecticides which act like lubricating oil and sink deep into insects exoskeletons or even into treated surfaces leaving a long lastin residue.

     

    Its actually a very interesting subject and the amount of different methods poisons and pesticides kill by is so diverse.

     

    Good luck in your research!

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