Advantage and disadvantage of chemical control of insects
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The use of chemical pesticides is widespread due to their relatively low cost, the ease with which they can be applied and their effectiveness, availability and stability. Chemical pesticides are generally fast-acting, which limits the damage done to crops.
Chemical pesticides have some major drawbacks, but they are still widely sold and used. We will discuss four of the disadvantages of chemical pesticides here. First, chemical pesticides are often not just toxic to the organisms for which they were intended, but also to other organisms. Chemical pesticides can be subdivided into two groups: non-selective and selective pesticides. The non-selective products are the most harmful, because they kill all kinds of organisms, including harmless and useful species. For example, there are herbicides that kill both broad-leaf weeds and grasses. This means they are non-selective since they kill nearly all vegetation.
Selective pesticides have a more limited range. They only get rid of the target pest, disease or weed and other organisms are not affected. An example is a weed killer that only works on broadleaf weeds. This could be used on lawns, for example, since it does not kill grass. These days, a combination of several products is usually required to control several pests because almost all permitted products are selective and thus only control a limited range of pests.
Another disadvantage of chemical pesticides is resistance. Pesticides are often effective for only a (short) period on a particular organism. Organisms can become immune to a substance, so they no longer have an effect. These organisms mutate and become resistant. This means that other pesticides need to be used to control them.
A third drawback is accumulation. If sprayed plants are eaten by an organism, and that organism is then eaten by another, the chemicals are can be passed up the food chain. Animals at the top of the food chain, usually predators or humans, have a greater chance of toxicity due to the build-up of pesticides in their system. Gradually, however, this effect is becoming less relevant because pesticides are now required to break down more quickly so that they cannot accumulate. If they do not, they are not permitted for sale.