Insecticides parasites

One reason for the rapid growth in the use of pesticides worldwide has been the "Green Revolution" (5), Although there have been some benefits from pesticide use in agriculture, they also cause significant environmental and public health problems. The same is true in public health where Insecticides have been used to control malaria. However, today Increased resistance to insecticides in mosquitoes and Increased resistance to drugs by the malarial parasite are resulting in an explosive increase of malaria worldwide (5). 

The cyclodiene insecticides aldrin, dieldrin, endrin, heptachlor, endosulfan, and others were introduced in the early 1950s. They were used to control a variety of pests, parasites, and, in developing countries, certain vectors of disease such as the tsetse fly. However, some of them (e.g., dieldrin) combined high toxicity to vertebrates with marked persistence and were soon found to have serious side effects in the field, notably in Western European countries where they were extensively used. During the 1960s, severe restrictions were placed on cyclodienes so that few uses remained by the 1980s. 

The widespread use of economic poisons has a definite impact on the animal complex on the face of the earth which provides our sustenance. Already we have seen the use of DDT for codling moth control on apples result in a relatively minor pest becoming a serious threat. The same material used as a wonder spray for fly control now fails, after a couple years of common usage, with the appearance of new, resistant strains of flies. Bees and other pollinating insects as well as helpful predators or parasites may be decimated and their important aid be lost by untimely or improper use of most of the newer insecticides. 

Systemic insecticides are superior to contact insecticides in many ways. On account of their absorption and transfer in the plant they can deal with insects which might normally remain hidden or protected from the direct spray of a contact insecticide. Many systemic insecticides are specific to certain pests. For example, owing to the insecticide being contained within the plant, parasitic non-phytophagous insects are less likely than the pests to absorb the insecticide. And so ecological selectivity1 comes into play. 

The same sort of balance must be maintained in the use of insecticides. DDT furnished an excellent example in Florida. It killed the young scale insects, but it also killed so many of the parasites and predators that terrific scale populations resulted, which were difficult to bring under control. Obviously, selective insecticides are needed, which kill only injurious insects. Lacking this perfect answer, however, insecticides are used which are relatively less damaging to the friendly insects as compared to their effect on deleterious insects. 

Adverse hygienic conditions favor human infestation with multicellular organisms (referred to here as parasites). Skin and hair are colonization sites for arthropod ectoparasites, such as insects (lice, fleas) and arachnids (mites). Against these, insecticidal or arachnici-dal agents, respectively, can be used. Endoparasites invade the intestines or even internal organs, and are mostly members of the phyla of flatworms and roundworms. They are combated with anthelmintics. 

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