Insecticides predators

The effects of pollution can be direct, such as toxic emissions providing a fatal dose of toxicant to fish, animal life, and even human beings. The effects also can be indirect. Toxic materials which are nonbiodegradable, such as waste from the manufacture of insecticides and pesticides, if released to the environment, are absorbed by bacteria and enter the food chain. These compounds can remain in the environment for long periods of time, slowly being concentrated at each stage in the food chain until ultimately they prove fatal, generally to predators at the top of the food chain such as fish or birds. 

Many of the components of PCB and PBB mixtures are both lipophilic and stable, chemically and biochemically. Similar to the persistent organochlorine insecticides and their stable metabolites, they can undergo strong bioconcentration and bioaccumulation to reach relatively high concentrations in predators. 

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. 

DDT met all but one of Muller s ideal characteristics for an insecticide. It was a cheap, contact poison without objectionable odors. It was stable in air and light. Because it was so powerful, extremely small doses could be used. And finally, it dissolved so poorly in water that warm-blooded organisms absorbed only traces of it. The fact that DDT dissolves well in oils did not seem dangerous only later did scientists realize that, because DDT accumulates in animal fat and mammals milk, it becomes increasingly more concentrated in predator species as it moves up the food chain. DDT s only failing, as far as Muller s original conception was concerned, was that it did not kill immediately. 

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. 

There is evidence, moreover, that higher population densities and increased survival of some insect pests follow chemical treatments designed to control them. This is because such treatments result in the destruction of predator insects that naturally control pest populations. Killing the predators only increases the needs for future insecticide treatments. ... 

Look out for aphids on young shoots and leaves from spring onward. Squash these by hand or spray with insecticidal soap. Sow flowers to attract aphid predators (see p.95). 

What to do Encourage natural predators. Do not overfeed plants. Pesticides Insecticidal soap plant oils. 

For example, the lack of good alternatives pushed the U.S. Department of Agriculture in 1998 to recommend the use of methyl bromide to treat wood packaging materials from China. A voracious, nonnative insect pest had been found in such packaging materials in 14 states around the United States. The Asian beetle had no known U.S. predators and could cost the United States more than 41 billion in lost forest product, commercial fruit, maple syrup, nursery, and tourist industries. This beetle was an extremely serious insect, and methyl bromide was the only known effective insecticide. Heat treatment was also suggested, but it proved to be more difficult and expensive (Morse 1998). Therefore, methyl bromide as an insecticide was receiving a reprieve. 

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